Forms of rifaximin and uses thereof

ABSTRACT

Embodiments relate to Rifaximin polymorphic, salt, and hydrate forms, methods of producing polymorphic forms and to their use in medicinal preparations and to therapeutic methods using them.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/288,184, filed May 27, 2014, which is a continuation of U.S.application Ser. No. 13/949,684, filed Jul. 24, 2013, which is acontinuation of U.S. application Ser. No. 13/530,386, filed Jun. 22,2012, now U.S. Pat. No. 8,507,517, which is a continuation of U.S.application Ser. No. 13/434,766, filed Mar. 29, 2012, now U.S. Pat. No.8,227,482, which is a continuation of U.S. application Ser. No.13/371,238, filed Feb. 10, 2012, now U.S. Pat. No. 8,735,419, whichclaims benefit of U.S. Provisional Application Nos. 61/441,902, filedFeb. 11, 2011; 61/530,905, filed Sep. 2, 2011; 61/556,649, filed Nov. 7,2011; and 61/583,024, filed Jan. 4, 2012, each of which are incorporatedby reference herein in their entirety.

BACKGROUND

Rifaximin (INN; see The Merck Index, XIII Ed., 8304) is an antibioticbelonging to the rifamycin class of antibiotics, e.g., a pyrido-imidazorifamycin. Rifaximin exerts its broad antibacterial activity, forexample, in the gastrointestinal tract against localizedgastrointestinal bacteria that cause infectious diarrhea, irritablebowel syndrome, small intestinal bacterial overgrowth, Crohn's disease,and/or pancreatic insufficiency. It has been reported that rifaximin ischaracterized by a negligible systemic absorption, due to its chemicaland physical characteristics (Descombe J. J. et al. Pharmacokineticstudy of rifaximin after oral administration in healthy volunteers. IntJ Clin Pharmacol Res, 14 (2), 51-56, (1994)).

Rifaximin is described in Italian Patent IT 1154655 and EP 0161534, bothof which are incorporated herein by reference in their entirety for allpurposes. EP 0161534 discloses a process for rifaximin production usingrifamycin 0 as the starting material (The Merck Index, XIII Ed., 8301).U.S. Pat. No. 7,045,620 B1 and PCT Publication WO 2006/094662 A1disclose polymorphic forms of rifaximin, both of which are incorporatedherein by reference. U.S. Patent Publication US 2010-0239664 and US2010-0174064 and PCT Publication WO 2009/108730 also A1 disclosepolymorphic forms of Rifaximin, both of which are incorporated herein byreference.

The forms of rifaximin disclosed herein can be advantageously used aspure and homogeneous products in the manufacture of medicinalpreparations containing rifaximin.

SUMMARY

Embodiments described herein relate to the discovery of new polymorphicforms of rifaximin and the use of those forms as antibiotics. In someembodiments, polymorphic Forms of rifaximin of the antibiotic known asrifaximin (INN), in the manufacture of medicinal preparations for theoral or topical route is contemplated. Embodiments described herein alsorelate to administration of such medicinal preparations to a subject inneed of treatment with antibiotics.

According to one aspect, provided herein are polymorphic forms ofrifaximin, including Form Mu, Form Pi, Form Omicron, Form Zeta, FormEta, Form Iota, and salt forms and hydrates of rifaximin.

According to one aspect, the polymorphic forms of rifaximin describedherein are selected from one or more of Form Mu, Form Pi, Form Omicron,Form Zeta, Form Eta, Form Iota, salt forms, or hydrate forms, orcombinations thereof.

According to one aspect, the polymorphic form of rifaximin is Form Mu.In another aspect, the polymorphic form of rifaximin is Form Pi. Inanother aspect, the polymorphic form of rifaximin is Form Omicron. Inanother aspect, the polymorphic form of rifaximin is Form Zeta. Inanother aspect, the polymorphic form of rifaximin is Form Eta. Inanother aspect, the polymorphic form of rifaximin is Form Iota. Inanother aspect, the rifaximin is a salt form. In another aspect,rifaximin is a hydrate form.

According to one aspect, provided herein are pharmaceutical compositionscomprising at least one Form of rifaximin as described herein, with oneor more pharmaceutically acceptable carriers.

According to one aspect, provided herein are processes for producing theForms of rifaximin as described herein.

According to one aspect, provided herein are methods of treating,preventing, or alleviating diseases and disorders described herein,e.g., a bowel related disorder by administering at least one Form ofrifaximin as described herein.

According to one aspect, provided herein are packaged compositionscomprising at least one Form of rifaximin as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a XRPD pattern of rifaximin Form Mu.

FIG. 2 shows a XRPD pattern of rifaximin Form Mu with Observed Peakslisted.

FIG. 3 shows a XRPD pattern of rifaximin Form Mu with Observed Peakslisted.

FIG. 4 shows a tentative indexing solution for rifaximin Form Mu.

FIG. 5 shows a tentative indexing solution for rifaximin Form Mu.

FIG. 6A shows a DSC thermogram for rifaximin Form Mu and FIG. 6B shows aTGA thermogram for rifaximin Form Mu.

FIG. 7 shows moisture sorption (DVS) data of rifaximin Form Mu.

FIG. 8 shows post-DVS XRPD of rifaximin Form Mu.

FIG. 9 is an XRPD pattern illustrating the consistency of the patternfor rifaximin Form Pi.

FIG. 10 is a comparison of the XRPD pattern for rifaximin Form Pirelative to that of the other polymorphs of rifaximin.

FIG. 11 is a schematic of how the different polymorphs of rifaximin,including Form Pi, can be formed.

FIG. 12 is an XRPD pattern of different samples of rifaximin Form Pi.

FIG. 13 is an XRPD pattern of observed peaks for rifaximin Form Pi.

FIG. 14 is an XRPD pattern of observed peaks for rifaximin Form Pi.

FIG. 15 shows the variation between the relative intensities and peakpositions of the two prominent Bragg peaks of rifaximin Form Pi, due topreferred orientation of the faceted crystals.

FIG. 16 shows DSC and TGA thermograms of rifaximin Form Pi.

FIG. 17 shows moisture sorption (DVS) data of rifaximin Form Pi.

FIG. 18 shows the solution proton NMR spectrum of rifaximin Form Pi.

FIG. 19 shows the ATR-IR spectrum rifaximin Form Pi.

FIG. 20 shows the Raman spectrum of rifaximin Form Pi.

FIG. 21 shows the solid state carbon NMR spectrum of rifaximin Form Pi.

FIG. 22 shows a XRPD pattern of rifaximin Form Xi.

FIG. 23 shows a XRPD pattern of rifaximin Form Xi with Observed Peakslisted.

FIG. 24 shows a DSC thermogram of rifaximin Form Xi.

FIG. 25 shows a TGA thermogram of rifaximin Form Xi.

FIG. 26 shows moisture sorption (DVS) data of rifaximin Form Xi.

FIG. 27 shows a XRPD pattern of rifaximin Form Xi before and after theDVS experiment.

FIG. 28 shows a solution proton NMR spectrum of rifaximin Form Xi.

FIG. 29 shows a solid state carbon NMR spectrum of rifaximin Form Xi.

FIG. 30 shows an Infrared spectrum of rifaximin Form Xi.

FIG. 31 shows a Raman spectrum of rifaximin Form Xi.

FIG. 32 shows an indexing solution of rifaximin Form Omicron.

FIG. 33 shows the index unit cell parameters of rifaximin Form Omicron.

FIG. 34 shows an XRPD pattern of the observed peaks for rifaximin FormOmicron.

FIG. 35 shows DSC and TGA thermograms of rifaximin Form Omicron.

FIG. 36 shows moisture sorption (DVS) data of rifaximin Form Omicron.

FIG. 37 shows a XRPD pattern of rifaximin Form Omicron and post-DVSsample, Form Iota (t).

FIG. 38 shows an ATR-IR spectrum of rifaximin Form Omicron.

FIG. 39 shows a Raman spectrum of rifaximin Form Omicron.

FIG. 40 shows solution proton NMR spectrum of rifaximin Form Omicron.

FIG. 41 shows a solid state carbon NMR spectrum of rifaximin FormOmicron.

FIG. 42 is an exemplary XRPD Pattern of rifaximin Form Zeta.

FIG. 43 depicts an exemplary XRPD pattern of rifaximin Form Zeta.

FIG. 44 is an exemplary XRPD pattern of rifaximin Form Eta.

FIG. 45 depicts an exemplary XRPD pattern of rifaximin Form Eta.

FIG. 46 depicts an exemplary XRPD pattern of rifaximin Form Iota.

FIG. 47 depicts an exemplary background subtracted XRPD pattern ofrifaximin, Form Iota.

FIG. 48 depicts list of observed peaks for rifaximin, Form Iota. Notethat the peak labels are meant as a visual aid. Consult FIG. 49 foraccurate 2θ positions.

FIG. 49A depicts peaks for rifaximin, Form Iota and 49B depictsprominent peaks for rifaximin, Form Iota.

FIG. 50 depicts exemplary results of DSC and TGA thermograms forrifaximin, Form Iota.

FIGS. 51A and 51B depict exemplary results of hot stage microscopy ofrifaximin, Form Iota.

FIG. 52 depicts a FT-IR spectrum of rifaximin, Form Iota.

FIG. 53 shows an exemplary process for preparing rifaximin Forms Iotaand Eta.

DETAILED DESCRIPTION

Rifaximin is a compound of the rifamycin class of antibiotics. Rifaximinis a compound having the structure of Formula I:

Rifaximin is observed to crystallize in multiple crystalline forms, manyof which are variable multi-component crystals. The majority of theforms have been identified as variable and non-stoichiometric systems,where the unit cell volume can change to accommodate varying amounts ofsolvent and/or water.

Rifaximin is approved for the treatment of pathologies caused bynon-invasive strains of Escherichia coli, a micro-organism which is notable to penetrate into GI mucosa and therefore remains in contact withgastrointestinal fluids. In respect to possible adverse events coupledto the therapeutic use of rifaximin, the induction of bacterialresistance to the antibiotics is of particular relevance.

From this point of view, any differences found in the systemicabsorption of the forms of rifaximin disclosed herein can besignificant, because at sub-inhibitory concentration of rifaximin, suchas in the range from about 0.1 to about 1 mg/ml, selection of resistantmutants has been demonstrated to be possible (Marchese A. et al. “Invitro activity of rifaximin, metronidazole and vancomycin againstclostridium difficile and the rate of selection of spontaneouslyresistant mutants against representative anaerobic and aerobic bacteria,including ammonia-producing species.” Chemotherapy, 46(4), 253-266(2000)).

Polymorphs of rifaximin have been found to have differing in vivobioavailability properties. Thus, the polymorphs disclosed herein can beuseful in the preparation of pharmaceuticals with differentcharacteristics for the treatment of infections. This allows generationof rifaximin preparations that have significantly different levels ofadsorption with C_(max) values from about 0.0 ng/ml to about 5.0 μg/ml.This leads to preparation of rifaximin compositions that are fromnegligibly to significantly adsorbed by subjects undergoing treatment.

Thus, in one aspect, a method of modulating the therapeutic action ofrifaximin is provided, comprising selecting the proper polymorphic form,or mixture of forms, for treatment of a patient. For example, in thecase of invasive bacteria, the most bioavailable polymorphic form can beselected from those disclosed herein, whereas in the case ofnon-invasive pathogens, less adsorbed forms of rifaximin can be selectedsince they can be safer for the subject undergoing treatment. Forms ofrifaximin can determine solubility, which can also determinebioavailability.

As used herein, “rifaximin Form x,” “Form x” “Form x of rifaximin,”“polymorph x,” “Form x (y),” “Form y” and “rifaximin x” and variationsthereof, where x is Mu, Pi, Omicron, Zeta, Eta, Xi, or Iota, and yrepresents the corresponding Greek characters (μ), (π), (o), (ζ), (η),(ξ), and (ι), are used interchangeably to denote the polymorphic formsof rifaximin as further described herein by, for example, one or morepeaks of an x-ray diffractogram or differential scanning calorimetrydata. Forms of rifaxmin as described herein comprise x-ray powderdiffraction pattern peak positions as denoted in the Tables, Examplesand Figures disclosed herein.

As used herein, the term polymorph is occasionally used as a generalterm in reference to the forms of rifaximin and includes within thecontext, salt, hydrate, and polymorph co-crystal forms of rifaximin.This use depends on context and will be clear to one of skill in theart.

As used herein, the term “about” when used in reference to x-ray powderdiffraction pattern peak positions refers to the inherent variability ofthe peaks depending on, for example, the calibration of the equipmentused, the process used to produce the polymorph, the age of thecrystallized material and the like, and/or the instrumentation used. Inthis case the measurement variability of the instrument was about ±0.2degrees 2−θ, which is consistent with the USP definition for peakposition error. A person skilled in the art, having the benefit of thisdisclosure, would understand the use of “about” in this context. Theterm “about” in reference to other defined parameters, e.g., watercontent, C_(max), t_(max), AUC, intrinsic dissolution rates,temperature, and time, indicates the inherent variability in, forexample, measuring the parameter or achieving the parameter. A personskilled in the art, having the benefit of this disclosure, wouldunderstand the variability of a parameter as connoted by the use of theword “about.”

As used herein, “similar” in reference to a form exhibitingcharacteristics similar to, for example, an XRPD, an IR, a Ramanspectrum, a DSC, TGA, NMR, SSNMR, etc, indicates that the polymorph isidentifiable by that method and could range from similar tosubstantially similar, so long as the material is identified by themethod with variations expected by one of skill in the art according tothe experimental variations, including, for example, instruments used,time of day, humidity, season, pressure, room temperature, etc.

Polymorphism, as used herein, refers to the occurrence of differentcrystalline forms of a single compound in distinct hydrate status, e.g.,a property of some compounds and complexes. Thus, polymorphs aredistinct solids sharing the same molecular formula, yet each polymorphcan have distinct physical properties. Therefore, a single compound cangive rise to a variety of polymorphic forms where each form hasdifferent and distinct physical properties, such as solubility profiles,melting point temperatures, hygroscopicity, particle shape, density,flowability, compactibility and/or x-ray diffraction peaks. Thesolubility of each polymorph can vary, thus, identifying the existenceof pharmaceutical polymorphs is desirable for providing pharmaceuticalswith consistent and reproducible solubility profiles. It is desirable toinvestigate all solid state forms of a drug, including all polymorphicforms, and to determine the stability, dissolution and flow propertiesof each polymorphic form. Polymorphic forms of a compound can bedistinguished in a laboratory by X-ray diffractometry and by othermethods such as infrared spectroscopy. For a general review ofpolymorphs and the pharmaceutical applications of polymorphs see G. M.Wall, Pharm Manuf. 3, 33 (1986); J. K. Haleblian and W. McCrone, JPharm. Sci., 58, 911 (1969); and J. K. Haleblian, J. Pharm. Sci., 64,1269 (1975), each of which is incorporated herein by reference in itsentirety.

As used herein, “subject” includes organisms which are capable ofsuffering from a bowel disorder or other disorder treatable by rifaximinor who could otherwise benefit from the administration of a rifaximin asdescribed herein, such as human and non-human animals. Preferred humananimals include human subjects. The term “non-human animals” includesall vertebrates, e.g., mammals, e.g., rodents, e.g., mice, andnon-mammals, such as non-human primates, e.g., sheep, dog, cow,chickens, amphibians, reptiles, etc. Susceptible to a bowel disorder ismeant to include subjects at risk of developing a bowel disorderinfection, e.g., subjects suffering from one or more of an immunesuppression, subjects that have been exposed to other subjects with abacterial infection, physicians, nurses, subjects traveling to remoteareas known to harbor bacteria that causes travelers' diarrhea, subjectswho drink amounts of alcohol that damage the liver, subjects with ahistory of hepatic dysfunction, etc.

The language “a prophylactically effective amount” of a compound refersto an amount of a Form of rifaximin described herein, or otherwise asdescribed herein which is effective, upon single or multiple doseadministration to the subject, in preventing or treating a bacterialinfection.

The language “therapeutically effective amount” of a compound refers toan amount of an agent which is effective, upon single or multiple doseadministration to the subject to provide a therapeutic benefit to thesubject. In some embodiments, the therapeutic benefit is inhibiting avirus, or in prolonging the survivability of a subject with such a viralinfection. In some embodiments, the therapeutic benefit is inhibiting abacterial infection or prolonging the survival of a subject with such abacterial infection beyond that expected in the absence of suchtreatment.

For XRPD analysis, accuracy and precision associated with measurementson independently prepared samples on different instruments can lead tovariability which is greater than ±0.2° 2θ.

The rifaximin Forms described herein may also be characterized by unitcell volume. One of skill in the art would be able to determine majorpeaks and uniquely identifying peaks of the polymorphs of rifaximinusing the information set forth herein as well as the peak lists andXPRD patterns and data.

In one embodiment, Form Mu of rifaximin comprises an XRPD substantiallysimilar to one or more of FIGS. 1-3.

In one embodiment, Form Mu of rifaximin comprises a DSC or TGAthermogram substantially similar to FIG. 6.

In one embodiment, Form Mu of rifaximin comprises the peaks listed inTables 12-15.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ comprisingone or more peaks listed in FIG. 2 and/or FIG. 3.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 4.79, about 6.29, about 6.94, about 7.44, about7.84, about 8.11, about 8.36, about 8.55, about 8.70, about 8.88, about9.60, about 10.15, about 10.32, about 10.88, about 11.02, about 11.20,about 12.09, about 12.54, about 12.79, about 12.96, about 13.42, about13.63, about 13.86, about 14.54, about 14.90, about 15.25, about 15.50,about 16.00, about 16.30, about 16.62, about 16.78, about 16.97, about17.27, about 17.47, about 17.57, about 17.84, about 18.20, about 18.57,about 18.97, about 19.42, about 19.88, about 20.78, about 21.76, about22.18, about 22.52, about 22.83, about 23.27, about 23.70, about 24.17,about 24.47, about 24.67, about 25.26, about 25.81, about 26.53, about26.98, about 27.55, about 28.23, about 28.50, about 28.87, and about29.15.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 4.79, and about 6.29.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 4.79, and about 7.44.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 4.79, and about 8.11.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 8.11, and about 10.32.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 6.94, and about 11.20.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 4.79, and about 12.09.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about4.72, about 4.79, about 7.84, about 8.11, about 8.36, about 8.55, about8.70, about 9.60, and about 12.54.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 4.79, about 6.29, about 6.94, about 7.44, about7.84, about 8.11, about 8.36, about 8.55, about 8.70, about 8.88, andabout 9.60.

In one embodiment, Form Mu of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two moreof about 4.72, about 4.79, about 6.29, about 6.94, about 7.44, about7.84, about 8.11, about 8.36, about 8.55, about 8.70, about 8.88, about9.60, about 10.15, about 10.32, about 10.88, about 11.02, and about11.20.

In one embodiment, Form Pi of rifaximin comprises an X-ray powderdiffraction pattern substantially similar to that of FIG. 9.

In one embodiment, Form Pi of rifaximin comprises an X-ray powderdiffraction pattern substantially similar to that of FIG. 12.

In one embodiment, Form Pi of rifaximin comprises an X-ray powderdiffraction pattern substantially similar to that of FIG. 13.

In one embodiment, Form Pi of rifaximin comprises an X-ray powderdiffraction pattern substantially similar to that of FIG. 14.

In one embodiment, Form Pi of rifaximin comprises relative intensitiesand peak positions of two prominent Bragg peaks substantially similar tothat of FIG. 15.

In one embodiment, Form Pi of rifaximin comprises a DSC thermogramsubstantially similar to that of FIG. 16.

In one embodiment, Form Pi of rifaximin comprises moisture sorption data(DVS) substantially similar to that of FIG. 17.

In one embodiment, Form Pi of rifaximin comprises a solution proton NMRspectra substantially similar to that of FIG. 18.

In one embodiment, Form Pi of rifaximin comprises an ATR-IR spectrumsubstantially similar to that of FIG. 19.

In one embodiment, Form Pi of rifaximin comprises a Raman spectrumsubstantially similar to that of FIG. 20.

In one embodiment, Form Pi of rifaximin comprises a solid state carbonNMR spectrum substantially similar to that of FIG. 21.

In one embodiment, Form Pi of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about6.91 and about 7.16.

In one embodiment, Form Pi of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about6.91, about 7.16, and about 9.15.

In one embodiment, Form Pi of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about7.05 and about 7.29.

In one embodiment, Form Pi of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about7.05, about 7.29, and about 9.33.

In one embodiment, Form Pi of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about6.91-7.05 and about 7.16-7.29.

In one embodiment, Form Pi of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about6.91-7.05, about 7.16-7.29, and about 9.15-9.33.

In one embodiment, Form Omicron of rifaximin comprises an XRPDsubstantially similar to FIG. 32.

In one embodiment, Form Omicron of rifaximin comprises an XRPDsubstantially similar to FIG. 34.

In one embodiment, Form Omicron of rifaximin comprises index unit cellparameters substantially similar to that of FIG. 33.

In one embodiment, Form Omicron of rifaximin comprises DSC and TGAthermograms substantially similar to that of FIG. 35.

In one embodiment, Form Omicron of rifaximin comprises moisture sorptiondata (DVS) substantially similar to that of FIG. 36.

In one embodiment, Form Omicron of rifaximin comprises moisture sorptiondata (DVS) of rifaximin Form Omicron and post-DVS sample, Form Iotasubstantially similar to that of FIG. 37.

In one embodiment, Form Omicron of rifaximin comprises an ATR-IRspectrum substantially similar to that of FIG. 38.

In one embodiment, Form Omicron of rifaximin comprises a Raman spectrumsubstantially similar to that of FIG. 39.

In one embodiment, Form Omicron of rifaximin comprises a solution protonNMR spectrum substantially similar to that of FIG. 40.

In one embodiment, Form Omicron of rifaximin comprises a solid statecarbon NMR spectrum substantially similar to that of FIG. 41.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 7.77.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 8.31.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 8.47.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 9.13.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 9.58.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 9.74.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 12.35.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 13.27.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, and about 13.69.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, about 8.31, about 9.13, and about 13.27.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, about 8.31, about 9.13, about 13.27, andabout 13.69.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, about 8.31, about 9.13, about 13.27,about 13.69, and about 17.67.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, about 7.77, about 8.31, about 9.13,about 13.27, about 13.69, and about 17.67.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, about 8.31, about 9.13, about 9.58,about 9.74, about 13.27, about 13.69, and about 17.67.

In one embodiment, Form Omicron of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.87, about 6.99, about 7.77, about 8.31, about 8.47,about 9.13, about 9.58, about 9.74, about 10.86, about 12.35, about13.27, about 13.69, about 14.01, about 14.44, about 14.79, about 15.19,about 15.33, about 15.68, about 15.94, about 16.04, about 16.31, about16.66, about 17.00, about 17.35, about 17.67, about 18.08, about 19.04,about 19.24, about 19.52, about 19.85, about 20.17, about 20.42, about20.76, about 21.07, about 21.28, about 21.61, about 21.83, about 22.14,about 22.36, about 22.65, about 22.93, about 23.20, about 23.46, about23.71, about 24.15, about 24.35, about 24.67, about 25.07, about 25.40,about 25.80, about 26.22, about 26.54, about 26.76, about 27.17, about27.78, about 28.69, about 28.88, about 29.21, about 29.46, about 23.71,about 24.15, about 24.35, about 24.67, about 25.07, about 25.40, about25.80, about 26.22, about 26.54, about 26.76, about 27.17, about 27.78,about 28.69, about 28.88, about 29.21, and about 29.46.

In one embodiment, Form Zeta of rifaximin comprises an X-ray powderdiffraction pattern substantially similar to FIG. 42, and/or FIG. 43.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7, about 7.6, and about 9.5; or about 4.7, about 7.3,and about 8.2; or about 7.6, about 8.6, and about 10.5; or about 8.2,about 8.6, and about 9.5; or about 10.2, about 12.6, and about 13.2; orabout 7.3, about 10.5, and about 12.9; or about 7.3, about 7.6, about8.2, about 8.6; or about 4.7, about 7.3, about 7.6, about 9.5, and about10.5; or about 8.2, about 8.6, about 9.5, about 10.2, and about 10.5; orabout 8.6, about 9.5, about 10.2, about 10.5, and about 11.2; or about4.7, about 6.3, about 6.4, about 7.3, about 7.6, about 8.2, about 8.6,about 9.5, about 10.2, about 10.5, about 11.2, about 11.9, about 12.2,about 12.6, about 12.9, about 13.2.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7 (doublet), about 7.6 (doublet), and about 9.5; orabout 4.7 (doublet), about 7.3, and about 8.2; or about 7.6 (doublet),about 8.6, and about 10.5; or about 8.2, about 8.6, and about 9.5; orabout 10.2 (triplet), about 12.6 (quintet), and about 13.2 (doublet); orabout 7.3, about 10.5, and about 12.9 (doublet); or about 7.3, about 7.6(doublet), about 8.2, about 8.6; or about 4.7 (doublet), about 7.3,about 7.6 (doublet), about 9.5, and about 10.5; or about 8.2, about 8.6,about 9.5, about 10.2 (triplet), and about 10.5; or about 8.6, about9.5, about 10.2 (triplet), about 10.5, and about 11.2 (doublet); orabout 4.7 (doublet), about 6.3, about 6.4, about 7.3, about 7.6(doublet), about 8.2, about 8.6, about 9.5, about 10.2 (triplet), about10.5, about 11.2 (doublet), about 11.9 (doublet), about 12.2 (weak),about 12.6 (quintet), about 12.9 (doublet), about 13.2 (doublet).

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7, about 7.6, and about 9.5; or about 4.7, about 7.3,and about 8.2.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7 (doublet), about 7.6 (doublet), and about 9.5; orabout 4.7 (doublet), about 7.3, and about 8.2.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.6, about 8.6, and about 10.5.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.6 (doublet), about 8.6, and about 10.5.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 8.2, about 8.6, and about 9.5.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 10.2, about 12.6, and about 13.2.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 10.2 (triplet), about 12.6 (quintet), and about 13.2(doublet).

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.3, about 10.5, and about 12.9.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.3, about 10.5, and about 12.9 (doublet).

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.3, about 7.6, about 8.2, and about 8.6.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.3, about 7.6 (doublet), about 8.2, and about 8.6.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7, about 7.3, about 7.6, about 9.5, and about 10.5.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7 (doublet), about 7.3, about 7.6 (doublet), about 9.5,and about 10.5.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 8.2, about 8.6, about 9.5, about 10.2, and about 10.5.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 8.2, about 8.6, about 9.5, about 10.2 (triplet), and about10.5.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 8.6, about 9.5, about 10.2, about 10.5, and about 11.2.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 8.6, about 9.5, about 10.2 (triplet), about 10.5, andabout 11.2 (doublet).

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7, about 6.3, about 6.4, about 7.3, about 7.6, about8.2, about 8.6, about 9.5, about 10.2, about 10.5, about 11.2, about11.9, about 12.2, about 12.6, about 12.9, and about 13.2.

In one embodiment, Form Zeta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 4.7 (doublet), about 6.3, about 6.4, about 7.3, about 7.6(doublet), about 8.2, about 8.6, about 9.5, about 10.2 (triplet), about10.5, about 11.2 (doublet), about 11.9 (doublet), about 12.2 (weak),about 12.6 (quintet), about 12.9 (doublet), and about 13.2 (doublet).

In one embodiment, Form Eta of rifaximin comprises an X-ray powderdiffraction pattern substantially similar to FIG. 44 and/or FIG. 45.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ, at two ormore of about 6.1, about 7.3, and about 7.5; or about 6.1, about 7.3,and about 7.9; or about 6.1, about 7.3, and about 8.8; or about 6.1,about 7.3, and about 12.7; or about 6.1, about 7.5, and about 8.8; orabout 6.1, about 7.5, and about 7.9; or about 5.3, about 6.1, and about7.3; or about 5.3, about 6.1, and about 7.9; or about 5.3, about 6.1,and about 12.7; or about 5.3, about 6.1, and about 7.5; or about 5.3,about 6.1, and about 8.8; or about 6.1, about 7.3, about 7.5, about 7.9,about 8.8, and about 12.7; or about 5.3, about 6.1, about 7.3, about7.5, about 7.9, about 8.8, and about 12.7; or about 5.3, about 6.1,about 7.3, about 7.9, about 8.8, and about 12.7; or about 5.3, about6.1, about 7.3, about 7.5, about 8.8, and about 12.7; or about 5.3,about 6.1, about 7.3, about 7.5, about 7.9, about 8.8, and about 12.7.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 6.1, about 7.3, and about 7.5; or about 6.1, about 7.3,and about 7.9.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 6.1, about 7.3, and about 8.8.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 6.1, about 7.3, and about 12.7.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 6.1, about 7.5, and about 8.8.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 6.1, about 7.5, and about 7.9.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, and about 7.3.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, and about 7.9.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, and about 12.7.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, and about 7.5.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, and about 8.8; or about 6.1, about 7.3,about 7.5, about 7.9, about 8.8, and about 12.7.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, about 7.3, about 7.5, about 7.9, about8.8, and about 12.7.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, about 7.3, about 7.9, about 8.8, and about12.7.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, about 7.3, about 7.5, about 8.8, and about12.7.

In one embodiment, Form Eta of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.3, about 6.1, about 7.3, about 7.5, about 7.9, about8.8, and about 12.7.

In one embodiment, Form Iota of rifaximin comprises an XRPD patternsubstantially similar to FIG. 46.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.9, and about 9.0; or about 12.7, about 13.9,and about 14.9; or about 5.9, about 7.9, and about 12.7; or about 5.9,about 9.0, and about 12.7; or about 5.9, about 13.9, and about 14.9±0.1;or about 5.9, about 7.9, and about 14.9; or about 9.0, about 12.7, andabout 14.9; or about 5.9, about 7.9, about 9.0, and about 14.9; or about5.9, about 7.9, about 9.0, and about 12.7; or about 5.9, about 7.9,about 9.0, about 12.7, about 13.9, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.4, about 7.9, and about 9.4.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.4, about 20.0, and about 20.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 13.9, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 20.0, about 20.9, and about 23.4.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 13.9, about 14.9, about 20.0, and about 20.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 7.4, about 12.7, about 13.9, and about 23.4.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.4, about 7.9, about 12.7, about 13.9, about14.9, about 20.0, about 20.9, and about 23.4.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.4, about 7.9, about 9.0, about 9.4, about12.7, about 13.9, about 14.9, about 20.0, about 20.9, and about 23.4.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 13.9, about 14.9, about 20.0, and about 20.9;or about 5.9, about 13.9, and about 14.9; or about 7.4, about 12.7,about 13.9, and about 23.4; or about 20.0, about 20.9, and about 23.4;or about 5.9, about 7.4, about 7.9, about 12.7, about 13.9, about 14.9,about 20.0, about 20.9, and about 23.4; or about 5.9, about 7.4, about7.9, and about 9.4; or about 7.4, about 20.0, and about 20.9; or about5.9, about 7.4, about 7.9, about 9.0, about 9.4, about 12.7, about 13.9,about 14.9, about 20.0, about 20.9, and about 23.4.

In one embodiment, Form Iota exhibits an X-ray powder diffractionpattern comprising peaks expressed in degrees 2θ at two or more of about5.9, about 7.9, about 9.0, about 12.7, about 13.9, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.9, and about 9.0.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 12.7, about 13.9, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.9, and about 12.7.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 9.0, and about 12.7.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about5.9, about 13.9, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.9, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at about9.0, about 12.7, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.9, about 9.0, and about 14.9.

In one embodiment, Form Iota of rifaximin exhibits an X-ray powderdiffraction pattern comprising peaks expressed in degrees 2θ at two ormore of about 5.9, about 7.9, about 9.0, and about 12.7.

In one embodiment, Form Iota of rifaximin comprises DSC and TGAthermograms substantially similar to FIG. 50.

In one embodiment, Form Iota of rifaximin comprises solution proton NMRspectrum substantially similar to FIG. 53.

In one embodiment, provided herein are mixtures of the disclosedpolymorphic forms of rifaximin. For example, provided herein is Form Xi,which is a mixture of Form Omicron and Form Pi.

In one embodiment, the Form mu, Form pi, Form Omicron, Form Xi, Formzeta, Form eta, Form iota, or salt form of rifaximin contain less than5% by weight total impurities.

In one embodiment, the Form Mu, Form Pi, Form Omicron, Form Xi, FormZeta, Form Eta, Form Iota, or salt form of rifaximin are at least 50%pure, or at least 75% pure, or at least 80% pure, or at least 90% pure,or at least 95% pure, or at least 98% pure.

In one embodiment, the pharmaceutical composition comprises one or moreof Form Mu, Form Pi, Form Omicron, Form Xi, Form Zeta, Form Eta, FormIota, or salt form of rifaximin and a pharmaceutically acceptablecarrier.

In one embodiment, the composition further comprises one or morepharmaceutically acceptable excipients. The excipients may be one ormore of a diluting agent, binding agent, lubricating agent,disintegrating agent, coloring agent, flavoring agent or sweeteningagent.

In one embodiment, the pharmaceutical composition may be formulated ascoated or uncoated tablets, hard or soft gelatin capsules, sugar-coatedpills, lozenges, wafer sheets, pellets or powders in a sealed packet. Ina related embodiment, the pharmaceutical composition may also beformulated for topical use.

In one embodiment, provided herein are methods of treating, preventingor alleviating a bowel related disorder comprising administering to asubject in need thereof an effective amount of one or more of Form Mu,Form Pi, Form Omicron, Form Xi, Form Zeta, Form Eta, Form Iota, or saltform of rifaximin.

In one embodiment, provided herein are methods for treating irritablebowel syndrome in a subject. Irritable bowel syndrome (IBS) is adisorder that affects the motility (muscle contractions) of the colon.Sometimes called “spastic colon” or “nervous colitis,” IBS is notcharacterized by intestinal inflammation. IBS is a functional boweldisorder characterized by chronic abdominal pain, discomfort, bloating,and alteration of bowel habits. IBS may begin after an infection(post-infectious, IBS-PI) or without any other medical indicators.

In one embodiment, the subject is suffering from at least one bowelrelated disorder. Bowel related disorders include, for example, one ormore of irritable bowel syndrome (IBS), diarrhea, microbe associateddiarrhea, infectious diarrhea, Clostridium, Clostridium difficiledisease, travelers' diarrhea, small intestinal bacterial overgrowth(SIBO), Crohn's disease, diverticular disease, pancreatitis (includingchronic), pancreatic insufficiency, enteritis, colitis (including,ulcerative colitis), antibiotic associated colitis, hepaticencephalopathy (or other diseases which lead to increased ammonialevels), gastric dyspepsia, cirrhosis, polycystic liver disease,pouchitis, peritonitis, inflammatory bowel disease, H. pylori infection.

In one embodiment, the subject is suffering from at least one bowelrelated disorder selected from the group consisting of irritable bowelsyndrome, travelers' diarrhea, small intestinal bacterial overgrowth,Crohn's disease, chronic pancreatitis, pancreatic insufficiency,enteritis and colitis.

The length of treatment for a particular bowel disorder will depend inpart on the disorder. For example, travelers' diarrhea may only requiretreatment duration of from about 12 to about 72 hours, while Crohn'sdisease may require treatment durations from about 2 days to 3 months.Dosages of rifaximin will also vary depending on the diseases state.

The identification of those subjects who are in need of prophylactictreatment for bowel disorder is well within the ability and knowledge ofone skilled in the art. Certain of the methods for identification ofsubjects which are at risk of developing a bowel disorder which can betreated by the subject method are appreciated in the medical arts, suchas family history, travel history and expected travel plans, thepresence of risk factors associated with the development of that diseasestate in the subject. A clinician skilled in the art can readilyidentify such candidate subjects, by the use of, for example, clinicaltests, physical examination and medical/family/travel history.

In one embodiment, provided herein are methods of treating, preventing,or alleviating bowel related disorders in a subject suffering fromhepatic insufficiency. Such methods include administering to a subjectin need thereof an effective amount of one or more of Form Mu, Form Pi,Form Omicron, Form Xi, Form Zeta, Form Eta, Form Iota, or salt form, ora pharmaceutically acceptable salt, solvate or hydrate thereof. Asubject “suffering from hepatic insufficiency” as used herein includessubjects diagnosed with a clinical decrease in liver function, forexample, due to hepatic encephalopathy, hepatitis, or cirrhosis. Hepaticinsufficiency can be quantified using any of a number of scalesincluding a model end stage liver disease (MELD) score, a Child-Pughscore, or a Conn score.

In one embodiment, provided herein are methods for treating orpreventing traveler's diarrhea in a subject. Traveler's diarrhea refersto gastrointestinal illness common amongst travelers. According to theCDC, travelers' diarrhea (TD) is the most common illness affectingtravelers. Each year between 20%-50% of international travelers, anestimated 10 million persons, develop diarrhea. The onset of travelers'diarrhea usually occurs within the first week of travel but may occur atany time while traveling, and even after returning home. Risk is oftendependent on destination though other risk factors are possible. Forexamples of the use of rifaximin to treat Travelers' diarrhea, seeInfante R M, et al. Clinical Gastroenterology and Hepatology. 2004,2:135-138 and Steffen R, M.D. et al. The American Journal ofGastroenterology. May 2003, Volume 98, Number 5, each of which isincorporated herein by reference in its entirety.

The illness usually results in increased frequency, volume, and weightof stool. Altered stool consistency also is common. A traveler mayexperience, for example, four to five loose or watery bowel movementseach day. Other commonly associated symptoms are nausea, vomiting,diarrhea, abdominal cramping, bloating, fever, urgency, and malaise.Most cases are benign and resolve in 1-2 days without treatment, and TDis rarely life-threatening. The natural history of TD is that 90% ofcases resolve within 1 week, and 98% resolve within 1 month.

Infectious agents are the primary cause of TD. The majority of cases arecaused by bacterial, viral or protozoan infection. Bacterialenteropathogens cause approximately 80% of TD cases. The most commoncausative agent isolated in countries surveyed has been enterotoxigenicEscherichia coli (ETEC). ETEC produce watery diarrhea with associatedcramps and low-grade or no fever. Besides ETEC and other bacterialpathogens, a variety of viral and parasitic enteric pathogens also arepotential causative agents. In some embodiments, the traveler's diarrheais caused by exposure to E. coli.

In some embodiments, provided herein are methods for treating orpreventing hepatic encephalopathy in a subject. Hepatic encephalopathy(portal-systemic encephalopathy, liver encephalopathy, hepatic coma) isa deterioration of brain function that occurs because toxic substancesnormally removed by the liver build up in the blood and reach the brain.Substances absorbed into the bloodstream from the intestine pass throughthe liver, where toxins are normally removed. In hepatic encephalopathy,toxins are not removed because liver function is impaired. Once in braintissue, the compounds produce alterations of neurotransmission thataffect consciousness and behavior. There are 4 progressive stages ofimpairment associated with HE that are defined by using the West Havencriteria (or Conn score) which range from Stage 0 (lack of detectablechanges in personality) to Stage 4 (coma, decerebrate posturing, dilatedpupils). In the earliest stages, the person's mood may change, judgmentmay be impaired, and normal sleep patterns may be disturbed. As thedisorder progresses, the person usually becomes drowsy and confused, andmovements become sluggish. Symptoms of hepatic encephalopathy caninclude impaired cognition, reduced alertness and confusion, a flappingtremor (asterixis), and a decreased level of consciousness includingcoma (e.g., hepatic coma), cerebral edema, and, possibly, death. Hepaticencephalopathy is commonly called hepatic coma or portal-systemicencephalopathy in the literature.

In one embodiment, provided herein are methods for alleviating thesymptoms of bloating, gas or flatulence in a subject. In anotherembodiment the symptoms of bloating, gas or flatulence are caused bybacterial exposure. In other embodiments, the symptoms of bloating, gasor flatulence are not caused by bacterial exposure.

In some embodiments, provided herein are methods of treating orpreventing a pathology in a subject suspected of being exposed to abiological warfare agent.

A method of assessing the efficacy of the treatment in a subjectincludes determining the pre-treatment level of intestinal bacterialovergrowth by methods well known in the art (e.g., hydrogen breathtesting, biopsy, sampling of the intestinal bacteria, etc.) and thenadministering a therapeutically effective amount of a rifaximinpolymorph to the subject. After an appropriate period of time (e.g.,after an initial period of treatment) from the administration of thecompound, e.g., about 2 hours, about 4 hours, about 8 hours, about 12hours, or about 72 hours, the level of bacterial overgrowth isdetermined again. The modulation of the bacterial level indicatesefficacy of the treatment. The level of bacterial overgrowth may bedetermined periodically throughout treatment. For example, the bacterialovergrowth may be checked every few hours, days or weeks to assess thefurther efficacy of the treatment. A decrease in bacterial overgrowthindicates that the treatment is efficacious. The method described may beused to screen or select subjects that may benefit from treatment with arifaximin polymorph.

In yet another aspect, a method of treating a subject suffering from orsusceptible to a bowel disorder comprises administering to a subject inneed thereof a therapeutically effective amount of a rifaximin polymorphor co-crystal as described herein, to thereby treat the subject. Uponidentification of a subject suffering from or susceptible to a boweldisorder, for example, IBS, one or more rifaximin polymorphs areadministered.

Described herein are methods of using one or more of the Forms ofrifaximin described herein to treat vaginal infections, ear infections,lung infections, periodontal conditions, rosacea, and other infectionsof the skin and/or other related conditions.

Provided herein are vaginal pharmaceutical compositions to treat vaginalinfection, particularly bacterial vaginosis, to be administeredtopically, including vaginal foams and creams, containing atherapeutically effective amount of one for more polymorphic Forms ofrifaximin described herein, such as between about 25 mg and about 2500mg.

Pharmaceutical compositions known to those of skill in the art for thetreatment of vaginal pathological conditions by the topical route may beadvantageously used with one or more of the Forms of rifaximin describedherein. For example, vaginal foams, ointments, creams, gels, ovules,capsules, tablets and effervescent tablets may be effectively used aspharmaceutical compositions containing one or more of the Forms ofrifaximin described herein, which may be administered topically for thetreatment of vaginal infections, including bacterial vaginosis.

Also provided herein are methods of using one for more polymorphic Formsof rifaximin described herein to treat gastric dyspepsia, includinggastritis, gastroduodenitis, antral gastritis, antral erosions, erosiveduodenitis and peptic ulcers. These conditions may be caused by theHelicobacter pylori microorganism. Pharmaceutical formulations known bythose of skill in the art with the benefit of this disclosure to be usedfor oral administration of a drug may be used.

Provided herein are methods of treating ear infections with one for morepolymorphic Forms of rifaximin described herein. Ear infections includeexternal ear infection, or a middle and inner ear infection. Alsoprovided herein are methods of using one for more polymorphic Forms ofrifaximin described herein to treat or prevent aspiration pneumoniaand/or sepsis, including the prevention of aspiration pneumonia and/orsepsis in patients undergoing acid suppression or undergoing artificialenteral feedings via a Gastrostomy/Jejunostomy or naso/oro gastrictubes; prevention of aspiration pneumonia in patients with impairment ofmental status, for example, for any reason, for subjects undergoinganesthesia or mechanical ventilation that are at high risk foraspiration pneumonia. Provided herein are methods to treat or to preventperiodontal conditions, including plaque, tooth decay and gingivitis.Provided herein are methods of treating rosacea, which is a chronic skincondition involving inflammation of the cheeks, nose, chin, forehead, oreyelids.

In one aspect, methods of assessing the efficacy of treatment with arifaximin polymorph in a subject comprise determining the pre-treatmentlevel of bacterial overgrowth, administering a therapeutically effectiveamount of a rifaximin polymorph to the subject, and determining thebacterial overgrowth after an initial period of treatment with arifaximin polymorph, wherein the modulation of the bacterial overgrowthindicates efficacy of an anti-bacterial treatment.

Efficacy of a treatment may be measured for example, as reduction ofbacterial overgrowth. Efficacy may also be measured in terms of areduction of symptoms associated with the bowel disorder, astabilization of symptoms, or a cessation of symptoms associated with abowel disorder, for example, a reduction of nausea, bloating, diarrhea,and the like.

In one aspect, methods of monitoring the progress of a subject beingtreated with one or more rifaximin polymorphs comprise: determining thepre-treatment level of bacterial overgrowth; administering atherapeutically effective amount of a rifaximin polymorph describedherein to the subject; and determining the post-level of bacterialovergrowth after an initial period of treatment with one or more of therifaximin polymorphs described herein.

In one embodiment, the modulation of the bacterial overgrowth indicatesefficacy of an anti-bacterial treatment.

In another embodiment, a decrease in bacterial overgrowth indicates thatthe treatment is efficacious.

In another embodiment, the modulation of the bacterial overgrowth is anindication that the subject is likely to have a favorable clinicalresponse to the treatment.

Provided herein is the use of one or more of the Forms of rifaximindescribed herein as a medicament.

Embodiments also provide pharmaceutical compositions, comprising aneffective amount of a rifaximin polymorph (e.g., Form Mu, Form Pi, FormOmicron, Form Xi, Form Zeta, Form Eta, Form Iota, or salt form)described herein and a pharmaceutically acceptable carrier. In a furtherembodiment, the effective amount is effective to treat a bacterialinfection, e.g., small intestinal bacterial overgrowth, Crohn's disease,hepatic encephalopathy, antibiotic associated colitis, and/ordiverticular disease.

For examples of the use of rifaximin to treat Travelers' diarrhea, seeInfante R M, Ericsson C D, Zhi-Dong J, Ke S, Steffen R, Riopel L, Sack DA, DuPont, HL. Enteroaggregative Escherichia coli Diarrhea in Travelers:Response to Rifaximin Therapy. Clinical Gastroenterology and Hepatology.2004; 2:135-138; and Steffen R, M.D., Sack D A, M.D., Riopel L, Ph.D.,Zhi-Dong J, Ph.D., Sturchler M, M.D., Ericsson C D, M.D., Lowe B, M.Phil., Waiyaki P, Ph.D., White M, Ph.D., DuPont H L, M.D. Therapy ofTravelers' Diarrhea With Rifaximin on Various Continents. The AmericanJournal of Gastroenterology. May 2003, Volume 98, Number 5, all of whichare incorporated herein by reference in their entirety.

Embodiments also provide pharmaceutical compositions comprising one ormore of a Form Mu, Form Pi, Form Omicron, Form Xi, Form Zeta, Form Eta,Form Iota, or salt form of rifaximin, and a pharmaceutically acceptablecarrier. That is, formulations may contain only one polymorph or maycontain a mixture of more than one polymorph. Mixtures may be selected,for example on the basis of desired amounts of systemic adsorption,dissolution profile, desired location in the digestive tract to betreated, and the like. Embodiments of the pharmaceutical compositionfurther comprise excipients, for example, one or more of a dilutingagent, binding agent, lubricating agent, disintegrating agent, coloringagent, flavoring agent or sweetening agent. One composition may beformulated for selected coated and uncoated tablets, hard and softgelatin capsules, sugar-coated pills, lozenges, wafer sheets, pelletsand powders in sealed packet. For example, compositions may beformulated for topical use, for example, ointments, pomades, creams,gels and lotions.

In an embodiment, the rifaximin polymorph is administered to the subjectusing a pharmaceutically-acceptable formulation, e.g., apharmaceutically-acceptable formulation that provides sustained deliveryof the rifaximin polymorph to a subject for at least about 12 hours, 24hours, 36 hours, 48 hours, one week, two weeks, three weeks, or fourweeks after the pharmaceutically-acceptable formulation is administeredto the subject.

In certain embodiments, these pharmaceutical compositions are suitablefor topical or oral administration to a subject. In other embodiments,as described in detail below, the pharmaceutical compositions may bespecially formulated for administration in solid or liquid form,including those adapted for the following: (1) oral administration, forexample, drenches (aqueous or non-aqueous solutions or suspensions),tablets, boluses, powders, granules, pastes; (2) parenteraladministration, for example, by subcutaneous, intramuscular orintravenous injection as, for example, a sterile solution or suspension;(3) topical application, for example, as a cream, ointment or sprayapplied to the skin; (4) intravaginally or intrarectally, for example,as a pessary, cream or foam; or (5) aerosol, for example, as an aqueousaerosol, liposomal preparation or solid particles containing thecompound.

The phrase “pharmaceutically acceptable” refers to those rifaximinpolymorphs, compositions containing such compounds, and/or dosage formswhich are, within the scope of sound medical judgment, suitable for usein contact with the tissues of human beings and animals withoutexcessive toxicity, irritation, allergic response, or other problem orcomplication, commensurate with a reasonable benefit/risk ratio.

The phrase “pharmaceutically-acceptable carrier” includespharmaceutically-acceptable material, composition or vehicle, such as aliquid or solid filler, diluent, excipient, solvent or encapsulatingmaterial, involved in carrying or transporting the subject chemical fromone organ, or portion of the body, to another organ, or portion of thebody. Each carrier is preferably “acceptable” in the sense of beingcompatible with the other ingredients of the formulation and notinjurious to the subject. Some examples of materials which can serve aspharmaceutically-acceptable carriers include: (1) sugars, such aslactose, glucose and sucrose; (2) starches, such as corn starch andpotato starch; (3) cellulose, and its derivatives, such as sodiumcarboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4)powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients,such as cocoa butter and suppository waxes; (9) oils, such as peanutoil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil andsoybean oil; (10) glycols, such as propylene glycol; (11) polyols, suchas glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters,such as ethyl oleate and ethyl laurate; (13) agar; (14) bufferingagents, such as magnesium hydroxide and aluminum hydroxide; (15) alginicacid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer'ssolution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21)other non-toxic compatible substances employed in pharmaceuticalformulations.

Wetting agents, emulsifiers and lubricants, such as sodium laurylsulfate and magnesium stearate, as well as coloring agents, releaseagents, coating agents, sweetening, flavoring and perfuming agents,preservatives and antioxidants can also be present in the compositions.

Examples of pharmaceutically-acceptable antioxidants include: (1) watersoluble antioxidants, such as ascorbic acid, cysteine hydrochloride,sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2)oil-soluble antioxidants, such as ascorbyl palmitate, butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propylgallate, alpha-tocopherol, and the like; and (3) metal chelating agents,such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol,tartaric acid, phosphoric acid, and the like.

Compositions containing a rifaximin forms as disclosed herein includethose suitable for oral, nasal, topical (including buccal andsublingual), rectal, vaginal, aerosol and/or parenteral administration.The compositions may conveniently be presented in unit dosage form andmay be prepared by any methods well known in the art of pharmacy. Theamount of active ingredient which can be combined with a carriermaterial to produce a single dosage form will vary depending upon thehost being treated, the particular mode of administration. The amount ofactive ingredient which can be combined with a carrier material toproduce a single dosage form will generally be that amount of thecompound which produces a therapeutic effect. Generally, out of onehundred %, this amount will range from about 1% to about ninety-nine %of active ingredient, from about 5% to about 70%, and from about 10% toabout 30%.

Methods of preparing these compositions include the step of bringinginto association a rifaximin polymorph(s) with the carrier and,optionally, one or more accessory ingredients. In general, theformulations are prepared by uniformly and intimately bringing intoassociation a rifaximin polymorph with liquid carriers, or finelydivided solid carriers, or both, and then, if necessary, shaping theproduct.

Compositions suitable for oral administration may be in the form ofcapsules, cachets, pills, tablets, lozenges (using a flavored basis,usually sucrose and acacia or tragacanth), powders, granules, or as asolution or a suspension in an aqueous or non-aqueous liquid, or as anoil-in-water or water-in-oil liquid emulsion, or as an elixir or syrup,or as pastilles (using an inert base, such as gelatin and glycerin, orsucrose and acacia) and/or as mouth washes and the like, each containinga predetermined amount of a rifaximin polymorph(s) as an activeingredient. A compound may also be administered as a bolus, electuary orpaste.

Form μ, Form π, Form o, Form Xi, Form ζ, Form η, Form ι, or salt formscan be advantageously used in the production of medicinal preparationshaving antibiotic activity, containing rifaximin, for both oral andtopical use. The medicinal preparations for oral use will containrifaximin Form Mu, Form Pi, Form Omicron, Form Xi, Form Zeta, Form Eta,Form Iota, or salt forms together with the usual excipients, for examplediluting agents such as mannitol, lactose and sorbitol; binding agentssuch as starches, gelatines, sugars, cellulose derivatives, natural gumsand polyvinylpyrrolidone; lubricating agents such as talc, stearates,hydrogenated vegetable oils, polyethylenglycol and colloidal silicondioxide; disintegrating agents such as starches, celluloses, alginates,gums and reticulated polymers; colouring, flavouring and sweeteningagents.

In one embodiment, the composition is formulated for selected coated anduncoated tablets, hard and soft gelatine capsules, sugar-coated pills,lozenges, wafer sheets, pellets and powders in sealed packets.

Embodiments of the disclosure include solid preparations administrableby the oral route, for instance coated and uncoated tablets, of soft andhard gelatin capsules, sugar-coated pills, lozenges, wafer sheets,pellets and powders in sealed packets or other containers.

Medicinal preparations for topical use can contain rifaximin Form Mu,Form Pi, Form Omicron, Form Xi, Form Zeta, Form Eta, Form Iota, or saltform together with excipients, such as white petrolatum, white wax,lanoline and derivatives thereof, stearylic alcohol, propylene glycol,sodium lauryl sulfate, ethers of fatty polyoxyethylene alcohols, estersof fatty polyoxyethylene acids, sorbitan monostearate, glycerylmonostearate, propylene glycol monostearate, polyethylene glycols,methylcellulose, hydroxymethyl propylcellulose, sodiumcarboxymethylcellulose, colloidal aluminum and magnesium silicate,sodium alginate.

Embodiments of the disclosure relate to all of the topical preparations,for instance ointments, pomades, creams, gels and lotions.

In one embodiment, the compositions described herein are formulated fortopical use.

In solid dosage forms of rifaximin for oral administration (capsules,tablets, pills, dragees, powders, granules and the like), the activeingredient is typically mixed with one or morepharmaceutically-acceptable carriers, such as sodium citrate ordicalcium phosphate, and/or any of the following: (1) fillers orextenders, such as starches, lactose, sucrose, glucose, mannitol, and/orsilicic acid; (2) binders, such as, for example, carboxymethylcellulose,alginates, gelatin, polyvinyl pyrrolidone, sucrose and/or acacia; (3)humectants, such as glycerol; (4) disintegrating agents, such asagar-agar, calcium carbonate, potato or tapioca starch, alginic acid,certain silicates, and sodium carbonate; (5) solution retarding agents,such as paraffin; (6) absorption accelerators, such as quaternaryammonium compounds; (7) wetting agents, such as, for example, acetylalcohol and glycerol monostearate; (8) absorbents, such as kaolin andbentonite clay; (9) lubricants, such as talc, calcium stearate,magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate,and mixtures thereof; and (10) colouring agents. In the case ofcapsules, tablets and pills, the pharmaceutical compositions may alsocomprise buffering agents. Solid compositions of a similar type may alsobe employed as fillers in soft and hard-filled gelatin capsules usingsuch excipients as lactose or milk sugars, as well as high molecularweight polyethylene glycols and the like.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared usingbinder (for example, gelatin or hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (for example,sodium starch glycolate or cross-linked sodium carboxymethyl cellulose),surface-active or dispersing agent. Molded tablets may be made bymolding in a suitable machine a mixture of the powdered activeingredient moistened with an inert liquid diluent.

The tablets, and other solid dosage forms of the pharmaceuticalcompositions described herein, such as dragees, capsules, pills andgranules, may optionally be scored or prepared with coatings and shells,such as enteric coatings and other coatings well known in thepharmaceutical-formulating art. They may also be formulated so as toprovide slow or controlled release of the active ingredient thereinusing, for example, hydroxypropylmethyl cellulose in varying proportionsto provide the desired release profile, other polymer matrices,liposomes and/or microspheres. They may be sterilized by, for example,filtration through a bacteria-retaining filter, or by incorporatingsterilizing agents in the form of sterile solid compositions which canbe dissolved in sterile water, or some other sterile injectable mediumimmediately before use. These compositions may also optionally containopacifying agents and may be of a composition that they release theactive ingredient(s) only, or preferentially, in a certain portion ofthe gastrointestinal tract, optionally, in a delayed manner. Examples ofembedding compositions which can be used include polymeric substancesand waxes. The active ingredient can also be in micro-encapsulated form,if appropriate, with one or more of the above-described excipients.

Liquid dosage forms for oral administration of the rifaximinpolymorph(s) include pharmaceutically-acceptable emulsions,microemulsions, solutions, suspensions, syrups and elixirs. In additionto the active ingredient, the liquid dosage forms may contain inertdiluents commonly used in the art, such as, for example, water or othersolvents, solubilizing agents and emulsifiers, such as ethyl alcohol,isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol,benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils (inparticular, cottonseed, groundnut, corn, germ, olive, castor and sesameoils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fattyacid esters of sorbitan, and mixtures thereof.

In addition to inert diluents, the oral compositions can includeadjuvants such as wetting agents, emulsifying and suspending agents,sweetening, flavoring, coloring, perfuming and preservative agents.

Suspensions, in addition to the active rifaximin polymorph(s) maycontain suspending agents as, for example, ethoxylated isostearylalcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystallinecellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth,and mixtures thereof.

Pharmaceutical compositions for rectal or vaginal administration may bepresented as a suppository, which may be prepared by mixing one or morerifaximin polymorph(s) with one or more suitable nonirritatingexcipients or carriers comprising, for example, cocoa butter,polyethylene glycol, a suppository wax or a salicylate, and which issolid at room temperature, but liquid at body temperature and,therefore, will melt in the rectum or vaginal cavity and release theactive agent.

Compositions which are suitable for vaginal administration also includepessaries, tampons, creams, gels, pastes, foams or spray formulationscontaining such carriers as are known in the art to be appropriate.

Dosage forms for the topical or transdermal administration of arifaximin polymorph(s) include powders, sprays, ointments, pastes,creams, lotions, gels, solutions, patches and inhalants. The activerifaximin polymorph(s) may be mixed under sterile conditions with apharmaceutically-acceptable carrier, and with any preservatives,buffers, or propellants which may be required.

Ointments, pastes, creams and gels may contain, in addition to rifaximinpolymorph(s), excipients, such as animal and vegetable fats, oils,waxes, paraffins, starch, tragacanth, cellulose derivatives,polyethylene glycols, silicones, bentonites, silicic acid, talc and zincoxide, or mixtures thereof.

Powders and sprays can contain, in addition to a rifaximin polymorph(s),excipients such as lactose, talc, silicic acid, aluminum hydroxide,calcium silicates and polyamide powder, or mixtures of these substances.Sprays can additionally contain customary propellants, such aschlorofluorohydrocarbons and volatile unsubstituted hydrocarbons, suchas butane and propane.

The rifaximin polymorph(s) can be alternatively administered by aerosol.This is accomplished by preparing an aqueous aerosol, liposomalpreparation or solid particles containing the compound. A non-aqueous(e.g., fluorocarbon propellant) suspension could be used. Sonicnebulizers are preferred because they minimize exposing the agent toshear, which can result in degradation of the compound.

An aqueous aerosol is made, for example, by formulating an aqueoussolution or suspension of the agent together with conventionalpharmaceutically-acceptable carriers and stabilizers. The carriers andstabilizers vary with the requirements of the particular compound, buttypically include non-ionic surfactants (Tweens, Pluronics, orpolyethylene glycol), innocuous proteins like serum albumin, sorbitanesters, oleic acid, lecithin, amino acids such as glycine, buffers,salts, sugars or sugar alcohols. Aerosols generally are prepared fromisotonic solutions.

Transdermal patches have the added advantage of providing controlleddelivery of a rifaximin polymorph(s) to the body. Such dosage forms canbe made by dissolving or dispersing the agent in the proper medium.Absorption enhancers can also be used to increase the flux of the activeingredient across the skin. The rate of such flux can be controlled byeither providing a rate controlling membrane or dispersing the activeingredient in a polymer matrix or gel.

Ophthalmic formulations, eye ointments, powders, solutions and the like,are also contemplated as being within the scope of the invention.

Pharmaceutical compositions suitable for parenteral administration maycomprise one or more rifaximin polymorph(s) in combination with one ormore pharmaceutically-acceptable sterile isotonic aqueous or nonaqueoussolutions, dispersions, suspensions or emulsions, or sterile powderswhich may be reconstituted into sterile injectable solutions ordispersions just prior to use, which may contain antioxidants, buffers,bacteriostats, solutes which render the formulation isotonic with theblood of the intended recipient or suspending or thickening agents.

Examples of suitable aqueous and non-aqueous carriers which may beemployed in the pharmaceutical compositions include water, ethanol,polyols (such as glycerol, propylene glycol, polyethylene glycol, andthe like), and suitable mixtures thereof, vegetable oils, such as oliveoil, and injectable organic esters, such as ethyl oleate. Properfluidity can be maintained, for example, by the use of coatingmaterials, such as lecithin, by the maintenance of the required particlesize in the case of dispersions, and by the use of surfactants.

These compositions may also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofthe action of microorganisms may be ensured by the inclusion of variousantibacterial and antifungal agents, for example, paraben,chlorobutanol, phenol sorbic acid, and the like. It may also bedesirable to include isotonic agents, such as sugars, sodium chloride,and the like into the compositions. In addition, prolonged absorption ofthe injectable pharmaceutical form may be brought about by the inclusionof agents which delay absorption such as aluminum monostearate andgelatin.

In some cases, to prolong the effect of a drug, it is desirable to alterthe absorption of the drug. This may be accomplished by the use of aliquid suspension of crystalline or salt material having poor watersolubility. The rate of absorption of the drug may then depend on itsrate of dissolution which, in turn, may depend on crystal size andcrystalline form. Alternatively, delayed absorption of a drug form isaccomplished by dissolving or suspending the drug in an oil vehicle.

Injectable depot forms are made by forming microencapsule matrices ofrifaximin polymorph(s) in biodegradable polymers such aspolylactide-polyglycolide. Depending on the ratio of drug to polymer,and the nature of the particular polymer employed, the rate of drugrelease can be controlled. Examples of other biodegradable polymersinclude poly(orthoesters) and poly(anhydrides). Depot injectableformulations are also prepared by entrapping the drug in liposomes ormicroemulsions which are compatible with body tissue.

When the rifaximin polymorph(s) are administered as pharmaceuticals, tohumans and animals, they can be given per se or as a pharmaceuticalcomposition containing, for example, from about 0.1 to about 99.5% (forexample, from about 0.5 to about 90%) of active ingredient incombination with a pharmaceutically-acceptable carrier.

Regardless of the route of administration selected, the rifaximinpolymorph(s), which may be used in a suitable hydrated form, and/or thepharmaceutical compositions can be formulated intopharmaceutically-acceptable dosage forms by methods known to those ofskill in the art.

Actual dosage levels and time course of administration of the activeingredients in the pharmaceutical compositions may be varied so as toobtain an amount of the active ingredient which is effective to achievethe desired therapeutic response for a particular subject, composition,and mode of administration, without being toxic to the subject. Anexemplary dose range is from about 25 to about 3000 mg per day.

In one embodiment, the dose of rifaximin polymorph is the maximum that asubject can tolerate without developing serious side effects. In oneembodiment, the rifaximin polymorph is administered at a concentrationof about 1 mg to about 200 mg per kilogram of body weight, about10-about 100 mg/kg or about 40 mg-about 80 mg/kg of body weight. Rangesintermediate to the above-recited values are also intended to be part.

In combination therapy treatment, both the compounds of this inventionand the other drug agent(s) are administered to mammals (e.g., humans,male or female) by conventional methods. The agents may be administeredin a single dosage form or in separate dosage forms. Effective amountsof the other therapeutic agents are well known to those skilled in theart. However, it is well within the skilled artisan's purview todetermine the other therapeutic agent's optimal effective-amount range.In one embodiment in which another therapeutic agent is administered toan animal, the effective amount of the compound of this invention isless than its effective amount in case the other therapeutic agent isnot administered. In another embodiment, the effective amount of theconventional agent is less than its effective amount in case thecompound of this invention is not administered. In this way, undesiredside effects associated with high doses of either agent may beminimized. Other potential advantages (including without limitationimproved dosing regimens and/or reduced drug cost) will be apparent tothose skilled in the art.

In various embodiments, the therapies (e.g., prophylactic or therapeuticagents) are administered less than about 5 minutes apart, less than 30minutes apart, 1 hour apart, at about 1 hour apart, at about 1 to about2 hours apart, at about 2 hours to about 3 hours apart, at about 3 hoursto about 4 hours apart, at about 4 hours to about 5 hours apart, atabout 5 hours to about 6 hours apart, at about 6 hours to about 7 hoursapart, at about 7 hours to about 8 hours apart, at about 8 hours toabout 9 hours apart, at about 9 hours to about 10 hours apart, at about10 hours to about 11 hours apart, at about 11 hours to about 12 hoursapart, at about 12 hours to 18 hours apart, 18 hours to 24 hours apart,24 hours to 36 hours apart, 36 hours to 48 hours apart, 48 hours to 52hours apart, 52 hours to 60 hours apart, 60 hours to 72 hours apart, 72hours to 84 hours apart, 84 hours to 96 hours apart, or 96 hours to 120hours part. In preferred embodiments, two or more therapies areadministered within the same subject's visit.

In certain embodiments, one or more compounds and one or more othertherapies (e.g., prophylactic or therapeutic agents) are cyclicallyadministered. Cycling therapy involves the administration of a firsttherapy (e.g., a first prophylactic or therapeutic agent) for a periodof time, followed by the administration of a second therapy (e.g., asecond prophylactic or therapeutic agent) for a period of time,optionally, followed by the administration of a third therapy (e.g.,prophylactic or therapeutic agent) for a period of time and so forth,and repeating this sequential administration, i.e., the cycle in orderto reduce the development of resistance to one of the therapies, toavoid or reduce the side effects of one of the therapies, and/or toimprove the efficacy of the therapies.

In certain embodiments, the administration of the same compounds may berepeated and the administrations may be separated by at least about 1day, 2 days, 3 days, 5 days, 10 days, 15 days, 30 days, 45 days, 2months, 75 days, 3 months, or at least about 6 months. In otherembodiments, the administration of the same therapy (e.g., prophylacticor therapeutic agent) other than a rifaximin polymorph may be repeatedand the administration may be separated by at least about 1 day, 2 days,3 days, 5 days, 10 days, 15 days, 30 days, 45 days, 2 months, 75 days, 3months, or at least about 6 months.

Certain indications may require longer treatment times. For example,travelers' diarrhea treatment may only last from between about 12 hoursto about 72 hours, while a treatment for Crohn's disease may be frombetween about 1 day to about 3 months. A treatment for hepaticencephalopathy may be, for example, for the remainder of the subject'slife span. A treatment for IBS may be intermittent for weeks or monthsat a time or for the remainder of the subject's life.

Another embodiment includes articles of manufacture that comprise, forexample, a container holding a pharmaceutical composition suitable fororal or topical administration of rifaximin in combination with printedlabeling instructions providing a discussion of when a particular dosageform can be administered with food and when it should be taken on anempty stomach. Exemplary dosage forms and administration protocols aredescribed infra. The composition will be contained in any suitablecontainer capable of holding and dispensing the dosage form and whichwill not significantly interact with the composition and will further bein physical relation with the appropriate labeling. The labelinginstructions will be consistent with the methods of treatment asdescribed hereinbefore. The labeling may be associated with thecontainer by any means that maintain a physical proximity of the two, byway of non-limiting example, they may both be contained in a packagingmaterial such as a box or plastic shrink wrap or may be associated withthe instructions being bonded to the container such as with glue thatdoes not obscure the labeling instructions or other bonding or holdingmeans.

Another aspect is an article of manufacture that comprises a containercontaining a pharmaceutical composition comprising rifaximin wherein thecontainer holds preferably rifaximin composition in unit dosage form andis associated with printed labeling instructions advising of thediffering absorption when the pharmaceutical composition is taken withand without food.

Packaged compositions are also provided, and may comprise atherapeutically effective amount of rifaximin. Rifaximin and apharmaceutically acceptable carrier or diluent, wherein the compositionis formulated for treating a subject suffering from or susceptible to abowel disorder, and packaged with instructions to treat a subjectsuffering from or susceptible to a bowel disorder.

Kits are also provided herein, for example, kits for treating a boweldisorder in a subject. The kits may contain, for example, one or more ofForm Mu, Form Pi, Form Omicron, Form Xi, Form Zeta, Form Eta, Form Iota,or salt Form of rifaximin and instructions for use. The instructions foruse may contain proscribing information, dosage information, storageinformation, and the like.

Packaged compositions are also provided, and may comprise atherapeutically effective amount of one or more of a polymorph ofrifaximin as described herein and a pharmaceutically acceptable carrieror diluent, wherein the composition is formulated for treating a subjectsuffering from or susceptible to a bowel disorder, and packaged withinstructions to treat a subject suffering from or susceptible to a boweldisorder.

Exemplary methods of producing polymorphic forms of rifaximin are setforth below.

Embodiments are also directed to processes for producing one or more ofForm Mu, Form Pi, Form Omicron, Form Xi, Form Zeta, Form Eta, Form Iota,or salt Form of rifaximin. Methods are outlined in the Examples and inthe Tables infra.

In some embodiments, the rifaximin Forms are dried by air-drying atambient conditions. In some embodiments, the rifaximin Forms are driedwith a nitrogen bleed. In some embodiments, the rifaximin Forms aredried by vacuum drying at temperatures ranging from ambient temperature(about 25° C.) to about 60° C. In some embodiments, the rifaximin Formsare dried with agitation.

In some embodiments, the rifaximin Forms are obtained by drying therifaximin with ethanol under various drying conditions described herein.In some embodiments, the rifaximin Forms are obtained byrecrystallization from ethanol followed by one or more of the variousdrying conditions described herein.

In some embodiments, the water content of the ethanol described in theprocesses herein is less than about 10% (w/w), such as, less than about5% (w/w), less than about 2% (w/w), and less than about 1% (w/w). Insome embodiments, the ethanol is absolute.

In some embodiments, the method or process described herein includestirring at ambient temperatures.

In some embodiments, the method or process described herein includecollecting solids by filtration.

In some embodiments, the method or process described herein includedrying the collected solids.

Other embodiments and aspects are disclosed infra.

Rifaximin Form π can be prepared by drying absolute ethanol-dampRifaximin Form Omicron, or by a mixture of Form Omicron and Form Zeta.

Rifaximin Form Omicron can be prepared by slurrying Form Eta or FormGamma in ethanol to generate a slurry, which may be shaken andsubsequently filtered.

Rifaximin Form Eta and Iota can be prepared by the process according toFIG. 53. For example, provided herein is a least one method of preparingFrom Eta, comprising:

dissolving a Form of rifaximin to form a first mixture;

cooling the first mixture to a seeding temperature;

adding a slurry of rifaximin Form Zeta to form a second mixture;

cooling the second mixture to sub-ambient temperature; and

filtering the second mixture to obtain Form Eta, which is optionallywashed and dried.

In one aspect, the Form of rifaximin comprises a solid form. In anotheraspect, the Form of rifaximin is selected from Form Mu, Form Pi, Formalpha, Form beta, Form Xi, Form Nu, Form Theta, Form Gamma, FormOmicron, Form Zeta, or a salt, or mixtures thereof. In another aspect,the Form of rifaximin is Form Zeta.

In one aspect, the first mixture comprises ethanol. In another aspect,the water content of the first mixture is higher than approximately 3 wt%. In another aspect, the water content of the first mixture ranges fromabout 3 wt % to about 10 wt %.

Rifaximin Form μ can be prepared by fast evaporation from a 1:1 (v/v)ethanol/heptane solution at room temperature. In an exemplaryembodiment, approximately 3 grams of as-received material can bedissolved in about 60 mL ethanol. The solution can then be diluted withequal volume of heptane and filtered into an open beaker orcrystallization dish. The filtered solution can then be left at ambientconditions in a fume hood for fast evaporation.

Rifaximin Form Mu can also be generated through the hydration ofrifaximin Form Theta (which, in turn, is generated through thedesolvation of rifaximin Form Zeta).

Rifaximin Form Theta can convert to rifaximin Form μ upon exposure to75% RH. Additionally, rifaximin Form μ can be generated at 51% RH. Aslightly disordered Form μ (as a mixture with Form ι) can be generatedat 44% RH. Rifaximin Form μ can irreversibly dehydrate to Form γ.

Rifaximin Form gamma can be prepared by slurrying rifaximin in asolvent, e.g. ethanol, in a suitable reactor or flask that is equippedwith stirring, mechanical or magnetic, a thermometer and a refluxcondenser. The suspension is heated to a temperature of between about40° C. to about 80° C., e.g. between about 45° C. to about 70° C. orbetween about 55° C. to about 65° C., with stirring until completedissolution of the solid. While maintaining this temperature, a secondsolvent, e.g. water, is added over a period of about 1 minute to about120 minutes, e.g. about 10 minutes to about 60 minutes or about 20minutes to about 40 minutes. At the end of the addition of the secondsolvent the temperature is brought to between about 10° C. to about −50°C., e.g. from about 20° C. to about 40° C. or from about 25° C. to about35° C., over a period of time lasting between about 10 minutes to about120 minutes, e.g. about 20 minutes to about 60 minutes or about 30minutes to about 50 minutes, and is kept at this value untilcrystallization is observed. Subsequently, the temperature is lowered tobetween about −10° C. to about 10° C., e.g. between about −7° C. toabout 7° C. or between about −5° C. to about 5° C., over a period oftime lasting between about 0.5 hour to about 5 hours, e.g. about 1 hourto about 4 hours or about 1.5 hours to about 3 hours, and kept at thistemperature for between about 1 hour to about 24 hours, e.g. about 2hours to about 12 hours or about 4 hours to about 8 hours. Thesuspension is then filtered and the solid is washed with the secondsolvent, e.g. water. The filter cake is dried under vacuum at roomtemperature until a constant weight is observed.

Rifaximin Form Zeta can be prepared by suspending rifaximin in a mixtureof solvents, e.g. ethanol and water, with a ratio of about 4:1, attemperatures ranging from about 15° C. to about 35° C., e.g. from about20° C. to about 30° C. or from about 22° C. to about 27° C. for a periodof time ranging from about 1 hour to about 10 hours, e.g. about 2 hoursto about 8 hours or about 4 hours to about 6 hours. The solids can beisolated, e.g. via decantation or filtration, and the solids can bestored in a refrigerator.

In one embodiment, the process for producing Form ζ of rifaximincomprises forming an EtOH slurry of an initial Form α-dry of rifaximinat ambient temperature and crystallizing rifaximin from the slurry. Inone embodiment, the method further comprises crash cooling the slurryprior to crystallization. In another embodiment, the EtOH slurrycomprises an ethanol/water slurry in the ratio of from between 1 to0.02-0.45.

Rifaximin Form Theta can be prepared by drying Form ζ under vacuum atambient temperature for approximately 6 hours. Form Theta can be anethanolate based on ¹H-NMR results. In an exemplary embodiment, onesample can contain about two moles of ethanol per mole of rifaximin by¹H-NMR, but the volume estimated from the tentative XRPD indexingsolution indicates the unit cell is able to accommodate up to about 4moles of ethanol per mole of rifaximin. XRPD patterns of Form Theta wereindexed successfully. Successful indexing of the powder diffractionpattern exhibited by this form provides supports an indication that FormOmicron is a single crystalline phase. Rifaximin Form Theta can beobtained at large scale by vacuum drying of Form Zeta. In an exemplaryembodiment, about 58.96 g of rifaximin can be added to about 300 mL ofethanol with stirring at ambient conditions. The rifaximin can dissolvealmost completely in the initial stirring and yield a very dark redsolution. With continuous stirring, the solution can become lighter incolor, and the turbidity can increase until an orange/red paste isformed. At that point, an aliquot of about 100 mL of ethanol can beadded, producing a total volume of ethanol of about 400 mL. The slurrysample can then be vacuum filtered through a filter paper under nitrogenenvironment (21% RH, 22° C.) to produce a red-orange paste. Once thefiltrate stops dripping from the end of funnel, the filter cake can bebroken loose on the filter paper with a spatula while vacuum andnitrogen remain on. In the exemplary embodiment, the total drying timeof the sample on filter paper is approximately 30 minutes. The resultingsolid can be identified as Form Zeta by XRPD. This solid sample canlater be dried under vacuum for approximately 6 hours at ambienttemperature, and the post XRPD pattern can be used to confirm that thesolid has been converted to Form Theta after vacuum drying.

Rifaximin Form iota, can be prepared by precipitating rifaximin fromethanol; drying the precipitated rifaximin under nitrogen; andmaintaining the rifaximin at ambient temperature. In some embodiments,the rifaximin can be maintained under vacuum for about 6 or more hours.In some embodiments, the rifaximin can be maintained at between about22% and 50% humidity. In some embodiments, the rifaximin is dried forabout 10 minutes or less.

In one embodiment, methods for producing rifaximin Form Eta, comprise:

obtaining a rifaximin slurry in absolute ethanol;

heating the slurry to about 60° C. while stirring;

cooling the slurry to 40° C. while stirring;

adding a seed slurry of rifaximin to make a rifaximin mixture andstirring at 40° C.;

cooling the mixture to 0° C.;

holding the mixture at 0° C.;

vacuum filtering the mixture; and

vacuum oven drying,

thereby producing rifaximin Form Eta.

In a related embodiment, the stirring is at 300 RPM. In another relatedembodiment, the mixture is cooled to about 0° C. over a time of about200 minutes. In another related embodiment, the mixture is held at about0° C. for about 15 hours. In another related embodiment, the rifaximinseed mass is 1.5 weight % of the rifaximin slurry; the seed slurryconcentration is 3 times lower than the rifaximin slurry; the seedslurry concentration of approximately 50 mg/ml; or rifaximin slurry has20 times more ethanol than the rifaximin mass.

In yet another related embodiment, the vacuum oven drying is at about40° C. for about 24 hours.

In yet another related embodiment, the seed slurry comprises aconcentration of approximately 5 mg/ml rifaximin.

In one embodiment, processes for producing a mixture of polymorphs Zetaand gamma comprise humidifying Form Zeta.

In one embodiment, processes for producing Form η of rifaximin comprisedrying Form

Zeta.

In one embodiment, Form η and Iota are produced by the process disclosedin FIG. 11.

In one embodiment, processes of producing Zeta and mixtures of Zeta andGamma comprise precipitating the initial rifaximin forms.

In one embodiment, processes of producing mixtures of Form Gamma,including but not limited to, Form Gamma and Form Eta mixtures and FormGamma and Form Zeta mixtures comprise precipitating the initial forms.

In one embodiment, processes for producing rifaximin form Eta andmixtures of rifaximin forms η and γ comprise precipitating the initialrifaximin forms in the manner set forth in Table 22.

In one embodiment, processes for producing Form Eta, Form Zeta, FormGamma, Form Xi and Form Gamma mixtures and Form Gamma and Form Etamixtures of rifaximin comprise precipitating the initial forms in themanner set forth in Tables 24 and 25.

In one embodiment, processes for producing Form Iota comprise theconditions set forth in Table 28.

Some features of polymorph Form ζ include, for example:

Form Zeta was observed by XRPD analysis of solids in solution (FIGS. 42and 43). These solids were removed and stressed under various relativehumidity (RH) conditions. XRPD analysis after three days showedconversion to Form γ under 43% RH, though form conversion was likelyinitiated upon removal of the solids from solution.

Some features of polymorph Form Eta include, for example:

Form η was generated by drying Form Zeta under vacuum for one day (FIG.44). The material of Form Zeta (after formation) remained unchanged whendried under vacuum at 40° C. for one day.

Other exemplary protocols for making the disclosed polymorphic forms ofrifaximin can be found in the Examples as well as in U.S. Pat. No.7,045,620; U.S. Patent Publication No. 2009-0130201; U.S. PatentPublication No. 2011-0160449; U.S. Patent Publication No. 2010-0010028;U.S. Patent Publication No. 2011-0105550; and U.S. Patent PublicationNo. 2010-0174064, each of which is incorporated herein by reference inits entirety.

Further embodiments will now be described by the following non-limitingexamples. It will be appreciated that the invention should not beconstrued to be limited to any of the foregoing examples, which are nowdescribed.

EXAMPLES Materials

Samples were stored in a dessicator. Solvents and other reagents usedwere purchased from commercial suppliers and used as received. Solventswere either HPLC or ACS grade.

Example 1 Preparation of Form Xi

To prepare rifaximin Form Xi, 33.5 g rifaximin was first dried in vacuoat 40° C. for 16 hours and then dissolved in 150 mL absolute ethanol ina 500 mL jacketed reactor. With stirring, the mixture was heated 60° C.,held for 15 minutes and then cooled at 0.4° C./min to 40° C.Precipitation was visually observed at 43° C. The sample was heated backup to 60° C. to dissolve the solid and then cooled at 0.4° C./min to 45°C. The solution was seeded with a slurry of (500 mg) Form η in 10 mLethanol, that was pre-slurried for 4 hours. The mixture was heated at45° C. for 1 hour, then cooled to 0° C. over 200 minutes. The slurry washeld at 0° C. and continued stirring for 14 hours. The material wasfiltered, washed by 50 mL cold ethanol, and split equally into two lots.One lot was dried by rotary evaporation for 10 hours and the other lotwas vacuum dried for 20 hours.

The material was analyzed by x-ray powder diffractometry (XRPD). Inaddition, the material was characterized by differential scanningcalorimetry (DSC), thermogravimetric analysis (TGA), moisture sorption(also known as dynamic vapor sorption, DVS), Karl-Fischer titration(KF), solution proton (¹H) and solid-state (SS) nuclear magneticresonance (NMR), and attenuated total reflectance infrared (ATR-IR) andRaman spectroscopy.

The XRPD pattern of Rifaximin Form Xi is shown in FIGS. 22 and 23Observed and prominent peak lists are included.

One Panalytical pattern was analyzed. Observed peaks are shown in FIG.23

Additional characterization data for rifaximin Form Xi by DSC, TGA, DVSand XRPD before and after DVS are presented in FIG. 24 through FIG. 27.

DSC results show two broad endotherms with signal maxima atapproximately 73.9° C. and 203.2° C. TGA of the same sample indicates aweight loss of approximately 10.5% when heated up to 170° C. (FIG. 25.Thermal events above 230° C. are likely due to decomposition.

Rifaximin Form Xi contains 0.24 wt % of water by Karl-Fischer analysis.Solution ¹H-NMR shows that the sample contains approximately 2.1 mole ofethanol per mole of rifaximin.

Moisture sorption data for rifaximin Form Xi are shown in FIG. 26. Aninitial weight loss of 7.2% is observed upon equilibration at 5% RH. Thematerial exhibits a 7.9% weight gain from 5 to 95% RH and a 10.5% weightloss from 95 to 5% RH. The XRPD pattern of the specimen post-moisturesorption (FIG. 27) indicates the material became disordered.

Example 2 Preparation of Form Omicron

Rifaximin Form Omicron was prepared by three methods as described below.The sample generated by Method 1 was further characterized by DSC, TGA,DVS, Raman and ATR-IR spectroscopy, KF, and solution proton and solidstate carbon NMR spectrometry.

Method 1:

A slurry of Rifaximin Form Xi in absolute ethanol at 524 mg/mLconcentration was prepared and stirred at ambient temperature forapproximately one day. The slurry was filtered and characterized whiledamp with mother liquor by XRPD as Form Omicron.

Method 2:

A slurry of approximately equal masses of Rifaximin Form Xi and Form Etawas prepared in absolute ethanol at 230 mg/mL concentration. The mixturewas shaken at ˜1° C. for approximately seven days. The slurry wasfiltered and characterized while damp with mother liquor by XRPD as FormOmicron.

Method 3:

A slurry of approximately equal masses of Rifaximin Form Xi and FormGamma was prepared in absolute ethanol at 209 mg/mL concentration. Themixture was shaken at ˜1° C. for approximately seven days. The slurrywas filtered and characterized while damp with mother liquor by XRPD asForm Omicron.

Rifaximin Form Omicron was characterized by high resolution XRPD, DSC,TGA, DVS, Raman and ATR-IR spectroscopy, KF analysis and solution ¹H-and solid state ¹³C NMR spectrometry. FIG. 33 shows the indexingsolution and the unit cell parameters for Form Omicron.

A list of XRPD peak positions for one XRPD pattern of Rifaximin FormOmicron is described. Observed and prominent peak lists are included,while representative and characteristic peak lists are not included. OnePanalytical XRPD pattern was analyzed. Observed peaks are shown in Table2, and prominent peaks are listed in Table 3.

The DSC thermogram shows one major broad endotherm at approximately81.3° C. (peak maximum) and a minor broad endotherm at 135.0° C. (peakmaximum) (see FIG. 35). TGA of the same sample indicates two weight losssteps of approximately 18.6 wt % between 26 and 90° C. and approximately4.0 wt % between 90 and 135° C. The thermal events above 200° C. arelikely due to decomposition.

DVS analysis on a moisture balance of the Rifaximin Form Omicron showsan initial weight loss of ˜15 wt % at 5% RH upon equilibration (see FIG.36). The material exhibited a weight gain of 6.2 wt % from 5 to 95% RHand a weight loss of 9.5 wt % from 5 to 95% RH. The sample post-DVS wascharacterized by XRPD as Form Iota with a significant amount of disorder(see FIG. 37).

The Form Omicron sample contained 4.74 wt % water by KF analysis whichmay be approximately equivalent to two moles of water. Solution ¹H NMRspectroscopy indicated that the sample contained one mole of ethanol permole of Rifaximin. The weight percentages of water and ethanol contentas indicated by KF analysis and the solution ¹H NMR spectrum, aresignificantly lower than the weight loss that is indicated in the TGthermogram. This may be a result of surface solvent loss from the samplebetween analyses as the TGA test was performed 14 days prior to the ¹HNMR test.

TABLE 1 Characterization of Rifaximin Form Omicron Sample ID AnalysisResult 1 XRPD Form Omicron 2 XRPD Form Omicron 3 XRPD Form Omicron DSCBroad major endo @ 81.3° C. (peak max) Broad endo @ 135.0° C. (peak max)TGA 18.7 wt % loss from 26 to 90° C. (~4 mol EtOH equivalent) 4.0 wt %loss from 90 to 135° C. (~2 mol water equivalent) DVS −15.0 wt % changeon equilibration at 5% RH 6.2 wt % gain from 5 to 95% RH 9.5 wt % lostfrom 95 to 5% RH KF 4.74 wt % water (~2 mol equivalent) Post-DVS XRPDForm Iota ATR-IR Spectrum acquired Raman Spectrum acquired ¹H NMR 6.0 wt% EtOH (~1 mol equivalent) SS ¹³C NMR Spectrum acquired

TABLE 2 Observed Peaks for Rifaximin Form Omicron °2θ d space (Å)Intensity (%)  5.87 ± 0.20 15.063 ± 0.531  100  6.99 ± 0.20 12.652 ±0.372  39  7.77 ± 0.20 11.375 ± 0.300  8  8.31 ± 0.20 10.644 ± 0.262  23 8.47 ± 0.20 10.434 ± 0.252  10  9.13 ± 0.20 9.691 ± 0.217 20  9.58 ±0.20 9.235 ± 0.197 8  9.74 ± 0.20 9.077 ± 0.190 8 10.86 ± 0.20 8.144 ±0.152 5 12.35 ± 0.20 7.166 ± 0.117 9 13.27 ± 0.20 6.672 ± 0.102 13 13.69± 0.20 6.469 ± 0.095 17 14.01 ± 0.20 6.323 ± 0.091 10 14.44 ± 0.20 6.134± 0.086 10 14.79 ± 0.20 5.989 ± 0.082 10 15.19 ± 0.20 5.832 ± 0.077 715.33 ± 0.20 5.782 ± 0.076 6 15.68 ± 0.20 5.653 ± 0.073 8 15.94 ± 0.205.559 ± 0.070 5 16.04 ± 0.20 5.524 ± 0.069 5 16.31 ± 0.20 5.434 ± 0.0675 16.66 ± 0.20 5.321 ± 0.064 10 17.00 ± 0.20 5.217 ± 0.062 6 17.35 ±0.20 5.112 ± 0.059 7 17.67 ± 0.20 5.021 ± 0.057 20 18.08 ± 0.20 4.906 ±0.054 8 19.04 ± 0.20 4.662 ± 0.049 12 19.24 ± 0.20 4.614 ± 0.048 7 19.52± 0.20 4.548 ± 0.047 10 19.85 ± 0.20 4.472 ± 0.045 8 20.17 ± 0.20 4.402± 0.044 9 20.42 ± 0.20 4.349 ± 0.043 18 20.76 ± 0.20 4.279 ± 0.041 721.07 ± 0.20 4.216 ± 0.040 16 21.28 ± 0.20 4.176 ± 0.039 11 21.61 ± 0.204.113 ± 0.038 15 21.83 ± 0.20 4.072 ± 0.037 11 22.14 ± 0.20 4.014 ±0.036 7 22.36 ± 0.20 3.976 ± 0.035 7 22.65 ± 0.20 3.927 ± 0.035 13 22.93± 0.20 3.879 ± 0.034 7 23.20 ± 0.20 3.835 ± 0.033 6 23.46 ± 0.20 3.791 ±0.032 8 23.71 ± 0.20 3.752 ± 0.031 7 24.15 ± 0.20 3.685 ± 0.030 7 24.35± 0.20 3.655 ± 0.030 5 24.67 ± 0.20 3.609 ± 0.029 7 25.07 ± 0.20 3.552 ±0.028 8 25.40 ± 0.20 3.506 ± 0.027 5 25.80 ± 0.20 3.453 ± 0.027 4 26.22± 0.20 3.399 ± 0.026 9 26.54 ± 0.20 3.359 ± 0.025 4 26.76 ± 0.20 3.332 ±0.025 5 27.17 ± 0.20 3.282 ± 0.024 7 27.78 ± 0.20 3.212 ± 0.023 4 28.69± 0.20 3.111 ± 0.021 5 28.88 ± 0.20 3.092 ± 0.021 6 29.21 ± 0.20 3.057 ±0.021 4 29.46 ± 0.20 3.032 ± 0.020 4 23.71 ± 0.20 3.752 ± 0.031 10024.15 ± 0.20 3.685 ± 0.030 39 24.35 ± 0.20 3.655 ± 0.030 8 24.67 ± 0.203.609 ± 0.029 23 25.07 ± 0.20 3.552 ± 0.028 10 25.40 ± 0.20 3.506 ±0.027 20 25.80 ± 0.20 3.453 ± 0.027 8 26.22 ± 0.20 3.399 ± 0.026 8 26.54± 0.20 3.359 ± 0.025 5 26.76 ± 0.20 3.332 ± 0.025 9 27.17 ± 0.20 3.282 ±0.024 13 27.78 ± 0.20 3.212 ± 0.023 17 28.69 ± 0.20 3.111 ± 0.021 1028.88 ± 0.20 3.092 ± 0.021 10 29.21 ± 0.20 3.057 ± 0.021 10 29.46 ± 0.203.32 0.020 7

TABLE 3 Prominent Peaks for Rifaximin Form Omicron °2θ d space (Å)Intensity (%)  5.87 ± 0.20 15.063 ± 0.531 100  6.99 ± 0.20 12.652 ±0.372 39  8.31 ± 0.20 10.644 ± 0.262 23  9.13 ± 0.20  9.691 ± 0.217 2013.27 ± 0.20  6.672 ± 0.102 13 13.69 ± 0.20  6.469 ± 0.095 17 17.67 ±0.20  5.021 ± 0.057 20

Example 3 Preparation of Form Pi

Method 1:

A reactor vessel was charged with a slurry of approximately 8.7 g ofRifaximin in 52 mL of absolute ethanol containing 0.9 wt % water(determined by Karl Fisher water analysis), that was prepared in advanceby stirring for approximately 45 minutes. Absolute ethanol (9 mL) wasused to rinse the slurry preparation container and added to the reactorvessel. The seed slurry was prepared by stirring 135.7 mg of Rifaximinin 1 mL of absolute ethanol for approximately 90 minutes. The seedslurry was added directly to the reactor as required. The slurry washeated to 55° C., cooled to 40° C., and then the seed slurry was addedand the reactor was held for stirring for one hour before cooling to 0°C. over 200 min. The slurry was held for approximately 2 hours at 0° C.After the crystallization, the slurry was discharged from the reactorvessel and immediately filtered to dry land using a Buchner filter andfunnel and grade 1 filter paper. The wet cake was dried in a vacuum ovenat ambient temperature for four days. Typical pressure values for thevacuum oven are about 40 to about 50 mTorr.

Method 2:

Form π was also prepared by drying a mixture of Rifaximin Forms Omicronand Zeta, damp with absolute ethanol, in a vacuum oven at approximately40° C. for 1 day. Typical pressure values for the vacuum oven are about40 to about 50 mTorr.

Method 3:

Rifaximin Form Beta was recrystallized from absolute ethanol bydissolving approximately 140 mg/mL in absolute ethanol at 55° C.Detailed methods of forming Beta are known in the art and can be foundin U.S. Pat. No. 7,045,620, which is incorporated by reference herein.The solution was then cooled to 40° C., seeded with approximately 1.5 wt% seed (with respect to Rifaximin input mass), that was prepared bydissolving approximately 140 mg/mL Rifaximin Form Eta in absoluteethanol. The slurry was cooled to 0° C. over 200 minutes then held forapproximately 2 hours before filtering and drying in a vacuum oven atambient temperature for approximately 4 days. Typical pressure valuesfor the vacuum oven are about 40 to about 50 mTorr. The dried solid wascharacterized by XRPD as Form Pi, and shown in FIGS. 9 and 12-14.

Rifaximin Form Pi appeared to be a variable solvate. The unit-cellparameters can expand or contract to accommodate the solvatecomposition. XRPD peak positions are a direct result of the unit cellparameters, and therefore one single XRPD pattern will not berepresentative of the crystal form. A list of XRPD peak positions isprovided for two XRPD patterns that represent the extremes of theunit-cell volumes for Rifaximin Pi and these two patterns were combinedto provide peak position ranges, listed in Table 10 and Table 11.Observed and prominent peak lists are included, while representative andcharacteristic peak lists are not included. Only one Panalytical XRPDpattern were collected. Observed peaks are shown in Table 6 and Table 8,and prominent peaks are listed in Tables 7 and 9.

To investigate if preferred orientation was present, two XRPD patternswere collected on the same undisturbed specimen from the coarser-grainedfraction of the sample. These grains appeared to have faceted surfacesby visual inspection with the unaided eye. XRPD patterns were collectedon this specimen using the Bragg-Brentano geometry and the transmissiongeometry to determine if preferred orientation was affecting therelative intensities of the sharp (Bragg) peaks. FIG. 15 showsconsiderable variation of the relative intensities and peak positions ofthe two prominent Bragg peaks. The variation of relative intensity ofthese closely positioned peaks indicates the presence of preferredorientation in this specimen and suggests specimens with facetedsurfaces are likely to display preferred orientation because the facetsare from single crystals of Form Pi. These two patterns also had thelowest diffuse background generated by disordered crystalline materialcompared to all other patterns collected on Form Pi samples.

The DSC thermogram shows one major broad endotherm with a peak maximumat 66.4° C. and a minor endotherm with a peak maximum at 203.4° C. (seeFIG. 16). TGA of the sample shows a weight loss of 2.49 wt % between 26and 80° C. that is likely associated with the first broad endothermicevent, and weight loss of 1.56 wt % between 80 and 203° C. The thermalevents above 203° C. are likely due to decomposition.

DVS analysis on a moisture balance of the Rifaximin Form Pi sample showsan initial weight loss of 1.3 wt % at 5% RH upon equilibration (see FIG.17). The material is reversibly hygroscopic and exhibited adsorption of10.5 wt % from 5 to 95% RH and desorption of 11.3% from 95 to 5% RH. Thematerial post-DVS analysis was characterized by XRPD as Form Pi.

The Form Pi sample was found to contain 1.67 wt % water by KF analysisthat is equivalent to approximately 0.75 moles of water per moleRifaximin. Solution proton NMR spectroscopy of the same sample wasconsistent with the Rifaximin structure with the presence ofapproximately 0.67 moles of ethanol per mole of Rifaximin. ATR-IR, Ramanspectra and solid-state ¹³C CP/MAS NMR spectra were also obtained. Thepeaks in the solid state ¹³C CP/MAS NMR spectra were broader than thosein the spectra when compared to known forms of rifaximin, whichindicates that Form Pi is disordered.

TABLE 4 Preparationof Rifaximin Pi Sample ID Analysis Preparation Method1 Pi (XRPD) Method 1 2 Pi (XRPD) Method 1 3 Pi (XRPD) Method 3 4 Pi(XRPD) Method 2 5 Pi (XRPD) Method 4 6 Pi (XRPD) Method 4 7 Pi (XRPD)Method 4

TABLE 5 Characterization of Rifaximin Pi Analysis Result XRPD PiXRPD^(a) Pi XRPD^(b) Pi DSC Broad major endo @ 66.4° C. (peak max) Broadendo @ 203.4° C. (peak max) TGA 2.5 wt % loss from 26 to 80° C. (~0.4mol EtOH equivalent) 1.6 wt % loss from 80 to 203° C. (~0.7 mol waterequivalent) DVS −1.3 wt % change on equilibration at 5% RH 10.5 wt %gain from 5 to 95% RH 11.3 wt % lost from 95 to 5% RH KF 1.67 wt %,~0.75 mol water Post-DVS XRPD Pi ATR-IR Spectrum acquired Raman Spectrumacquired ¹H NMR ~0.67 mol EtOH SS ¹³C NMR Spectrum acquired ^(a)Largeparticles were preferentially selected from top of sample afterhorizontal oscillation. Bragg-Brentano geometry. ^(b)RH ranged from 24to 27% during data collection. Transmission geometry.

TABLE 6 Observed peaks for Rifaximin Pi °2θ d space (Å) Intensity (%)6.91 ± 0.20 12.797 ± 0.381 93 7.16 ± 0.20 12.350 ± 0.355 100 9.15 ± 0.20 9.669 ± 0.216 44

TABLE 7 Prominent peaks for Rifaximin Pi °2θ d space (Å) Intensity (%)6.91 ± 0.20 12.797 ± 0.381 93 7.16 ± 0.20 12.350 ± 0.355 100

TABLE 8 Observed peaks for Rifaximin Pi °2θ d space (Å) Intensity (%)7.05 ± 0.20 12.532 ± 0.365 94 7.29 ± 0.20 12.130 ± 0.342 100 9.33 ± 0.20 9.483 ± 0.207 52

TABLE 9 Prominent peaks for Rifaximin Pi °2θ d space (Å) Intensity (%)7.05 ± 0.20 12.532 ± 0.365 94 7.29 ± 0.20 12.130 ± 0.342 100

TABLE 10 Observed peak ranges for Rifaximin Pi °2θ Range d space (Å)Range Intensity (%) Range (6.91 ± 7.05) ± 0.20 12.797 ± 0.381-12.532 ±0.365 93-94 (7.16 ± 7.29) ± 0.20 12.350 ± 0.355-12.130 ± 0.342 100 (9.15± 9.33) ± 0.20  9.669 ± 0.216-9.483 ± 0.207 44-52

TABLE 11 Prominent peak ranges for Rifaximin Pi °2θ Range d space (Å)Range Intensity (%) Range (6.91-7.05) ± 0.20 12.797 ± 0.381-12.532 ±0.365 93-94 (7.16-7.29) ± 0.20 12.350 ± 0.355-12.130 ± 0.342 100

Example 4 Preparation of Form Mu

Form Mu was obtained by fast evaporation of rifaximin in 1:1 (v/v)ethanol/heptane at ambient temperature. It was also shown that FormTheta will convert to Form μ upon exposure to 75% RH at ambienttemperature. Additionally, Form Zeta converts to Form Mu upon exposureto 51% RH at ambient temperature. Form μ irreversibly desolvates to FormGamma, when exposed to ˜60° C. under vacuum for ˜24 hours.

Approximately 3 grams of rifaximin was dissolved in 60 mL ethanol. Thesolution was then diluted with equal volume of heptane and filtered intoan open beaker or crystallization dish. The filtered solution was leftat ambient in a fume hood for fast evaporation.

Details of each experiment are presented in Table 12. For exampleRifaximin form Mu was prepared by first dissolving 3.2422 g of rifaximininto 60 mL ethanol. A red solution observed. The solution was thendiluted 1:1 with 60 mL heptane, mixed and filtered through a 0.2 μmNylon filter into an open crystallization dish. The crystallization dishwas left at ambient in fume hood for fast evaporation of solvent.Solvent evaporation was completed overnight and orange blades withbirefringence and extinction was produced.

Rifaximin Form μ is a variable solvated/hydrated crystalline form. It isgenerated through the hydration of Form Theta (which, in turn, isgenerated through the desolvation of Form ζ). Its crystal lattice canexpand or contract to accommodate changes in solvent and/or watercontent. The structure, with a calculated range for its volume performula unit between 1279 and 1293 Å3, contains voids estimated to bebetween approximately 252 and 266 Å3, respectively, that can be occupiedby solvent and/or water.

Characterization of various samples of Form μ is consistent with theknown variability in its solvent/water content. For example,approximately 0.6 moles of EtOH (per mole of rifaximin) and 12.7 wt %water was observed in one sample while approximately 0.5 moles of EtOHand 14.1 wt % water was observed in another sample.

Rifaximin Form Theta will convert to Form μ upon exposure to 75% RH.Additionally, Form μ was generated at 51% RH. A slightly disordered FormMu (as a mixture with Form Iota) was generated at 44% RH. Rifaximin Formμ irreversibly dehydrates to Form Gamma.

Rifaximin Form gamma can be prepared by slurrying rifaximin in asolvent, e.g. ethanol, in a suitable reactor or flask that is equippedwith stirring, mechanical or magnetic, a thermometer and a refluxcondenser. The suspension is heated at 40-80° C., e.g. 45° C. to 70° C.or 55° C. to 65° C., with stirring until complete dissolution of thesolid. While maintaining this temperature a second solvent, e.g. water,is added over 1-120 minutes, e.g. 10-60 minutes or 20-40 minutes. At theend of the addition of the second solvent the temperature is brought to10-50° C., e.g. 20° C. to 40° C. or 25° C. to 35° C., in 10-120 minutes,e.g. 20-60 minutes or 30-50 minutes, and is kept at this value untilcrystallization is observed, then the temperature is further lowered to−10-10° C., e.g. −7° C. to 7° C. or −5° C. to 5° C., over 0.5-5 hours,e.g. 1-4 hours or 1.5-3 hours, and kept at this temperature for 1-24hours, e.g. 2-12 hours or 4-8 hours. The suspension is then filtered andthe solid is washed with the second solvent, e.g. water. The filter cakeis dried under vacuum at room temperature until a constant weight isobserved.

Rifaximin Form Zeta can be prepared by suspending rifaximin in a mixtureof solvents, e.g. ethanol and water, with a ratio of 4:1, at 15° C. to35° C., e.g. 20° C. to 30° C. or 22° C. to 27° C. for 1-10 hours, e.g.2-8 hours or 466 hours. The solids are isolated, e.g. via decantation orfiltration, and the solids are stored in a refrigerator.

Rifaximin Form Theta was can be prepared by drying Form ζ under vacuumat ambient temperature for approximately 6 hours. Form Theta may be anethanolate based on 1H-NMR results. One sample contains two moles ofethanol per mole of rifaximin by 1H-NMR, but the volume estimated fromthe tentative XRPD indexing solution indicates the unit cell is able toaccommodate up to 4 moles of ethanol per mole of rifaximin. XRPDpatterns of Form Theta were indexed successfully. Successful indexing ofthe powder diffraction pattern exhibited by this form provides supportthat Form Theta is a single crystalline phase. Rifaximin Form Theta wasobtained at large scale by vacuum drying of Form ζ. In this Example,58.96 g of rifaximin was added to 300 mL of ethanol with stirring atambient condition. The rifaximin almost completely dissolved initiallyand yielded a very dark red solution. With continuous stirring, thesolution became lighter in color and turbidity increased until anorange/red paste was formed. At that point, another 100 mL of ethanolwas added. The total volume of ethanol was 400 mL. The slurry sample wasthen vacuum filtered through a filter paper under nitrogen environment(21% RH, 22° C.) and a red-orange paste was obtained. Once filtratestopped dripping from the end of funnel, the filter cake was brokenloose on the filter paper with a spatula while vacuum and nitrogen stillremained on. The total drying time of the sample on filter paper wasapproximately 30 minutes.

The resulting solid was identified as Form Zeta by XRPD. This solidsample was later dried under vacuum for approximately 6 hours at ambienttemperature. The post XRPD pattern confirms that the solid converted toForm Theta after vacuum drying.

Additional methods to prepare rifaximin Form Mu (as a pure phase or asmixtures with other forms), which did not utilize 1:1 (v/v)ethanol/heptane, are also known. These experiments are summarized inTable 12A. It was shown that Form Theta will convert at least partiallyto Form μ upon exposure to 75% RH. Additionally, Form Zeta converts toForm Mu upon exposure to 51% RH at ambient temperature. A slightlydisordered Form Mu (as a mixture with Form Iota) was generated fromethanol at 44% RH and ambient temperature.

The material was analyzed by x-ray powder diffractometry (XRPD) and thepatterns were indexed. In addition, the material was characterized bydifferential scanning calorimetry (DSC), thermogravimetric analysis(TGA), dynamic vapor sorption (DVS), Karl-Fischer titration (KF),solution proton (¹H-) and solid-state (SS-) nuclear magnetic resonance(NMR), and attenuated total reflectance infrared (ATR-IR) and Ramanspectroscopy.

The XRPD patterns of two Form μ samples are shown in FIG. 1. Since FormMu is a variable system with flexible unit cell structure that mayreadily expand or contract to accommodate various amounts of solvent, itshould be noted that the illustrated patterns are only representationsof two discrete examples of a series of peak ranges that may beexhibited by Form μ.

The list of peak positions for each XRPD pattern of rifaximin Form μillustrated in Table 13 is presented in FIG. 2 and FIG. 3, respectively.Observed and prominent peak lists are included in Tables 13-16.Representative and characteristic peak lists are not included. OnePANalytical pattern was analyzed for each sample.

The XRPD patterns of rifaximin Form Mu were indexed and are illustratedin FIG. 4 and FIG. 5. Indexing is the process of determining the sizeand shape of the unit cell given the peak positions in a diffractionpattern.

Agreement between the allowed peak positions, marked with bars in FIG. 4and FIG. 5, and the observed peaks indicates a consistent unit celldetermination. Successful indexing of the pattern indicates that eachsample is composed primarily of a single crystalline phase. Space groupsconsistent with the assigned extinction symbol, unit cell parameters,and derived quantities are tabulated in Table 17.

The volume of rifaximin (1027 Å³/molecule) was derived from a previouslyreported rifaximin hydrate structure. A typical value of 20 Å³/moleculewas used for water of hydration. Therefore, given the volume per formulaunit from the indexing solution for Form μ of 1293.4 Å³, approximately226 Å³ are available for water. Up to 13 moles of water per rifaximinare possible in the available volume. A second XRPD pattern of Form μwas also indexed with a volume per formula unit of 1278.5 Å³, and up to12.5 moles of water per rifaximin are possible in the available volume.Analysis of the actual Form μ samples by KF and ¹H-NMR shows that samplecontains approximately 0.5 mole of ethanol and 7 moles of water per moleof rifaximin, while an additional sample contains approximately 0.6 moleof ethanol and 6 moles of water per mole of rifaximin (Table 20).

The XRPD patterns listed above represent a single phase of rifaximin,designated as Form μ. Because Form μ is a variable solvate, the unitcell parameters may change via expansion or contraction to accommodatethe solvent. XRPD peak positions are a direct result of the unit cellparameters. Peak lists are presented for the two patterns above and arecombined in Table 18 and Table 19 to provide peak position ranges.

Additional characterization data for rifaximin Form Mu by DSC, TGA, DVSand XRPD before and after DVS are presented in FIG. 6 through FIG. 8,and are summarized in Table 20.

DSC result shows a broad endotherm with signal maximum at approximately92° C. and enthalpy change of 443.1 J/g. TGA of the same sampleindicates a weight loss of approximately 15.7% when heated up to 100° C.(FIG. 6).

Moisture sorption data for rifaximin Form μ are shown in FIG. 7. Aninitial weight loss of 11.0% was observed upon equilibration at 5% RH.The material exhibited a 9.5% weight gain from 5 to 95% RH and a 9.3%weight loss from 95 to 5% RH. The XRPD pattern of the specimenpost-moisture sorption (FIG. 8) indicates the material has converted toForm Gamma. The chemical composition of the specimen post-moisturesorption was not determined.

Other characterizations, including NMR, KF, ATR-IR, and Raman analysisresults are also summarized in Table 20.

Physical stability data is summarized in Table 21. Form μ irreversiblydesolvates to Form γ, a highly disordered form, when exposed to ˜60° C.under vacuum for ˜24 hours; this result was repeated in a separateexperiment. Form μ converted to Form Beta when the sample was exposed to97% RH at ambient temperature for ˜16 days.

The XRPD pattern of Form Mu was indexed successfully. Form Mu isidentified as a variable system of which the unit cell parameters maychange via expansion or contraction to accommodate the solvent. MultipleXRPD patterns obtained on various samples suggest that a range exist forthe reflection peaks observed in Form Mu. Indexing solutions wereobtained on two representative XRPD patterns of Form Mu but do notnecessarily indicate the upper and lower limit of the range. Rather theycan be considered two discrete examples of the Form Mu series.Theoretical calculation from the indexing solutions indicates that thetwo samples may be able to accommodate up to 12.5 or 13 moles of waterper mole of rifaximin based on the void space within the unit cell.Karl-Fischer analysis on the two Form μ samples shows that the materialcontains approximately 6 to 7 moles of water per mole of rifaximin.¹H-NMR analysis of the two indexed Form Mu sample shows that theycontain 0.5 to 0.6 mole of ethanol per mole of rifaximin.

TABLE 12 Preparation of Rifaximin Form μ EtOH/Heptane Rifaximin (1:1v/v, total XRPD (g) mL) Condition¹ Observation² result 3.2422 120 FE,RT, 1 Orange blades, μ day B/E 3.1467 120 FE, RT, 1 Orange blades, μ dayB/E 3.2548 120 FE, RT, 1 Red blades, B/E μ day 3.2354 120 FE, RT, 4 Redblades, B/E μ day 3.1974 120 FE, RT, 1 Red blades, B/E μ day 3.2557 120FE, RT, 1 Red blades, B/E μ day 3.1361 120 FE, RT, 1 Red blades, B/E μday 3.2052 120 FE, RT, 1 Red blades, B/E μ day μ 0.1441 6 FE, RT, 1Blades, B μ day ¹FE = fast evaporation; RT = room temperature. ²B =birefringent; E = extinction.

TABLE 12A Attempts to Prepare Rifaximin Form Mu through other MethodsMethod Observations Results precipitation from EtOH, bright orange- μ +ι isolated under 44% RH (RT) red disordered ζ exposed to 51% RH (RT),~20 bright orange μ min θ exposed to 75% RH (RT), 6 orange μ + ι hrs θexposed to 75% RH (40° C.), 6 orange μ + η hrs

TABLE 13 Observed Peaks for Rifaximin Form Mu Intensity °2θ d space (Å)(%)  4.72 ± 0.10 18.729 ± 0.405  100  4.79 ± 0.10 18.467 ± 0.394  84 6.29 ± 0.10 14.054 ± 0.227  7  6.94 ± 0.10 12.736 ± 0.186  10  7.44 ±0.10 11.879 ± 0.162  5  7.84 ± 0.10 11.272 ± 0.145  20  8.11 ± 0.1010.901 ± 0.136  55  8.36 ± 0.10 10.575 ± 0.128  32  8.55 ± 0.10 10.348 ±0.122  44  8.70 ± 0.10 10.169 ± 0.118  44  8.88 ± 0.10 9.959 ± 0.113 5 9.60 ± 0.10 9.215 ± 0.097 13 10.15 ± 0.10 8.716 ± 0.087 6 10.32 ± 0.108.575 ± 0.084 3 10.88 ± 0.10 8.128 ± 0.075 10 11.02 ± 0.10 8.030 ± 0.0739 11.20 ± 0.10 7.899 ± 0.071 11 12.09 ± 0.10 7.322 ± 0.061 3 12.54 ±0.10 7.059 ± 0.057 18 12.79 ± 0.10 6.922 ± 0.054 6 12.96 ± 0.10 6.833 ±0.053 6 13.42 ± 0.10 6.596 ± 0.049 5 13.63 ± 0.10 6.499 ± 0.048 9 13.86± 0.10 6.390 ± 0.046 19 14.54 ± 0.10 6.090 ± 0.042 21 14.90 ± 0.10 5.948± 0.040 16 15.25 ± 0.10 5.811 ± 0.038 6 15.50 ± 0.10 5.718 ± 0.037 816.00 ± 0.10 5.540 ± 0.035 14 16.30 ± 0.10 5.438 ± 0.033 10 16.62 ± 0.105.335 ± 0.032 8 16.78 ± 0.10 5.282 ± 0.031 6 16.97 ± 0.10 5.226 ± 0.0316 17.27 ± 0.10 5.135 ± 0.030 8 17.47 ± 0.10 5.077 ± 0.029 6 17.57 ± 0.105.048 ± 0.029 6 17.84 ± 0.10 4.973 ± 0.028 5 18.20 ± 0.10 4.873 ± 0.0279 18.57 ± 0.10 4.778 ± 0.026 13 18.97 ± 0.10 4.678 ± 0.025 24 19.42 ±0.10 4.570 ± 0.023 22 19.88 ± 0.10 4.467 ± 0.022 4 20.78 ± 0.10 4.275 ±0.020 16 21.76 ± 0.10 4.084 ± 0.019 10 22.18 ± 0.10 4.008 ± 0.018 1022.52 ± 0.10 3.949 ± 0.017 12 22.83 ± 0.10 3.895 ± 0.017 7 23.27 ± 0.103.823 ± 0.016 8 23.70 ± 0.10 3.754 ± 0.016 7 24.17 ± 0.10 3.682 ± 0.0159 24.47 ± 0.10 3.638 ± 0.015 8 24.67 ± 0.10 3.609 ± 0.014 7 25.26 ± 0.103.526 ± 0.014 12 25.81 ± 0.10 3.452 ± 0.013 7 26.53 ± 0.10 3.360 ± 0.01211 26.98 ± 0.10 3.305 ± 0.012 11 27.55 ± 0.10 3.238 ± 0.012 11 28.23 ±0.10 3.161 ± 0.011 7 28.50 ± 0.10 3.132 ± 0.011 6 28.87 ± 0.10 3.093 ±0.011 7 29.15 ± 0.10 3.064 ± 0.010 10

TABLE 14 Prominent Peaks for Rifaximin Form μ Intensity °2θ d space (Å)(%)  4.72 ± 0.10 18.729 ± 0.405 100  4.79 ± 0.10 18.467 ± 0.394 84  7.84± 0.10 11.272 ± 0.145 20  8.11 ± 0.10 10.901 ± 0.136 55  8.36 ± 0.1010.575 ± 0.128 32  8.55 ± 0.10 10.348 ± 0.122 44  8.70 ± 0.10 10.169 ±0.118 44  9.60 ± 0.10  9.215 ± 0.097 13 12.54 ± 0.10  7.059 ± 0.057 18

TABLE 15 Observed Peaks for Rifaximin Form μ Intensity °2θ d space (Å)(%)  4.75 ± 0.10 18.597 ± 0.400 99  4.82 ± 0.10 18.339 ± 0.388 100  6.32± 0.10 13.980 ± 0.224 8  6.96 ± 0.10 12.705 ± 0.185 14  7.46 ± 0.1011.852 ± 0.161 7  7.86 ± 0.10 11.248 ± 0.145 23  8.13 ± 0.10 10.879 ±0.135 77  8.39 ± 0.10 10.533 ± 0.127 60  8.56 ± 0.10 10.328 ± 0.122 53 8.73 ± 0.10 10.130 ± 0.117 57  8.90 ± 0.10  9.941 ± 0.113 8  9.65 ±0.10  9.167 ± 0.096 17 10.18 ± 0.10  8.687 ± 0.086 7 10.37 ± 0.10  8.533± 0.083 5 10.92 ± 0.10  8.104 ± 0.075 14 11.24 ± 0.10  7.875 ± 0.070 1412.12 ± 0.10  7.302 ± 0.061 5 12.59 ± 0.10  7.031 ± 0.056 15 12.84 ±0.10  6.895 ± 0.054 10 13.01 ± 0.10  6.807 ± 0.053 6 13.66 ± 0.10  6.483± 0.048 15 13.91 ± 0.10  6.367 ± 0.046 23 14.29 ± 0.10  6.197 ± 0.043 1614.54 ± 0.10  6.090 ± 0.042 33 14.95 ± 0.10  5.928 ± 0.040 23 15.28 ±0.10  5.799 ± 0.038 7 15.55 ± 0.10  5.700 ± 0.037 10 16.05 ± 0.10  5.523± 0.034 21 16.38 ± 0.10  5.411 ± 0.033 11 16.67 ± 0.10  5.319 ± 0.032 1016.87 ± 0.10  5.256 ± 0.031 11 17.03 ± 0.10  5.205 ± 0.031 9 17.35 ±0.10  5.111 ± 0.029 9 17.52 ± 0.10  5.062 ± 0.029 10 17.85 ± 0.10  4.968± 0.028 7 18.27 ± 0.10  4.856 ± 0.026 12 18.62 ± 0.10  4.765 ± 0.025 1519.02 ± 0.10  4.665 ± 0.024 24 19.49 ± 0.10  4.554 ± 0.023 22 20.23 ±0.10  4.390 ± 0.022 7 20.56 ± 0.10  4.320 ± 0.021 11 21.26 ± 0.10  4.179± 0.020 12 21.80 ± 0.10  4.077 ± 0.019 13 22.23 ± 0.10  3.999 ± 0.018 1522.63 ± 0.10  3.929 ± 0.017 12 22.92 ± 0.10  3.881 ± 0.017 9 23.32 ±0.10  3.815 ± 0.016 9 23.79 ± 0.10  3.741 ± 0.016 9 24.24 ± 0.10  3.672± 0.015 10 24.54 ± 0.10  3.628 ± 0.015 10 25.34 ± 0.10  3.515 ± 0.014 1425.89 ± 0.10  3.441 ± 0.013 8 26.41 ± 0.10  3.375 ± 0.013 12 26.61 ±0.10  3.350 ± 0.012 11 27.09 ± 0.10  3.291 ± 0.012 11 27.63 ± 0.10 3.229 ± 0.012 13 28.30 ± 0.10  3.154 ± 0.011 9 28.97 ± 0.10  3.083 ±0.010 10 29.25 ± 0.10  3.053 ± 0.010 11

TABLE16 Prominent Peaks for Rifaximin Form μ Intensity °2θ d space (Å)(%) 4.75 ± 0.10 18.597 ± 0.400 99 4.82 ± 0.10 18.339 ± 0.388 100 7.86 ±0.10 11.248 ± 0.145 23 8.13 ± 0.10 10.879 ± 0.135 77 8.39 ± 0.10 10.533± 0.127 60 8.56 ± 0.10 10.328 ± 0.122 53 8.73 ± 0.10 10.130 ± 0.117 579.65 ± 0.10  9.167 ± 0.096 17

TABLE 17 Tentative Indexing Solutions and Derived QuantitiesForm/Pattern Rifaximin, Form μ Family and Monoclinic Space Group P2₁(#4) Z′/Z 4/8 a (Å) 13.043 13.063 b (Å) 21.040 21.144 c (Å) 37.50237.697 α (deg) 90 90 β (deg) 96.36 96.42 γ (deg) 90 90 Volume (Å³/cell)10228.1 10346.8 V/Z (Å³/formula unit) 1278.5 1293.4

TABLE 18 Observed Peak Ranges for Rifaximin Form Mu Intensity Range °2θRange d Space Range (Å) (%)  (4.72-4.75) ± 0.10 18.597 ± 0.400-18.729 ±0.405  99-100  (4.79-4.82) ± 0.10 18.339 ± 0.388-18.467 ± 0.394  84-100 (6.29-6.32) ± 0.10 13.980 ± 0.224-14.054 ± 0.227 7-8  (6.94-6.96) ±0.10 12.705 ± 0.185-12.736 ± 0.186 10-14  (7.44-7.46) ± 0.10 11.852 ±0.161-11.879 ± 0.162 5-7  (7.84-7.86) ± 0.10 11.248 ± 0.145-11.272 ±0.145 20-23  (8.11-8.13) ± 0.10 10.879 ± 0.135-10.901 ± 0.136 55-77 (8.36-8.39) ± 0.10 10.533 ± 0.127-10.575 ± 0.128 32-60  (8.55-8.56) ±0.10 10.328 ± 0.122-10.348 ± 0.122 44-53  (8.70-8.73) ± 0.10 10.130 ±0.117-10.169 ± 0.118 44-57  (8.88-8.90) ± 0.10  9.941 ± 0.113-9.959 ±0.113 5-8  (9.60-9.65) ± 0.10  9.167 ± 0.096-9.215 ± 0.097 13-17(10.15-10.18) ± 0.10  8.687 ± 0.086-8.716 ± 0.087 6-7 (10.32-10.37) ±0.10  8.533 ± 0.083-8.575 ± 0.084 3-5 (10.88-10.92) ± 0.10  8.104 ±0.075-8.128 ± 0.075 10-14 (11.20-11.24) ± 0.10  7.875 ± 0.070-7.899 ±0.071 11-14 (12.09-12.12) ± 0.10  7.302 ± 0.061-7.322 ± 0.061 3-5(12.54-12.59) ± 0.10  7.031 ± 0.056-7.059 ± 0.057 15-18 (12.79-12.84) ±0.10  6.895 ± 0.054-6.922 ± 0.054  6-10 (12.96-13.01) ± 0.10  6.807 ±0.053-6.833 ± 0.053 6-6 (13.63-13.66) ± 0.10  6.483 ± 0.048-6.499 ±0.048  9-15 (13.86-13.91) ± 0.10  6.367 ± 0.046-6.390 ± 0.046 19-23(14.90-14.95) ± 0.10  5.928 ± 0.040-5.948 ± 0.040 16-23 (15.25-15.28) ±0.10  5.799 ± 0.038-5.811 ± 0.038 6-7 (15.50-15.55) ± 0.10  5.700 ±0.037-5.718 ± 0.037  8-10 (16.00-16.05) ± 0.10  5.523 ± 0.034-5.540 ±0.035 14-21 (16.30-16.38) ± 0.10  5.411 ± 0.033-5.438 ± 0.033 10-11(16.62-16.67) ± 0.10  5.319 ± 0.032-5.335 ± 0.032  8-10 (16.78-16.87) ±0.10  5.256 ± 0.031-5.282 ± 0.031  6-11 (16.97-17.03) ± 0.10  5.205 ±0.031-5.226 ± 0.031 6-9 (17.27-17.35) ± 0.10  5.111 ± 0.029-5.135 ±0.030 8-9 (17.47-17.52) ± 0.10  5.062 ± 0.029-5.077 ± 0.029  6-10(17.84-17.85) ± 0.10  4.968 ± 0.028-4.973 ± 0.028 5-7 (18.20-18.27) ±0.10  4.856 ± 0.026-4.873 ± 0.027  9-12 (18.57-18.62) ± 0.10  4.765 ±0.025-4.778 ± 0.026 13-15 (18.97-19.02) ± 0.10  4.665 ± 0.024-4.678 ±0.025 24-24 (19.42-19.49) ± 0.10  4.554 ± 0.023-4.570 ± 0.023 22-22(21.76-21.80) ± 0.10  4.077 ± 0.019-4.084 ± 0.019 10-13 (22.18-22.23) ±0.10  3.999 ± 0.018-4.008 ± 0.018 10-15 (22.52-22.63) ± 0.10  3.929 ±0.017-3.949 ± 0.017 12-12 (22.83-22.92) ± 0.10  3.881 ± 0.017-3.895 ±0.017 7-9 (23.27-23.32) ± 0.10  3.815 ± 0.016-3.823 ± 0.016 8-9(23.70-23.79) ± 0.10  3.741 ± 0.016-3.754 ± 0.016 7-9 (24.17-24.24) ±0.10  3.672 ± 0.015-3.682 ± 0.015  9-10 (24.47-24.54) ± 0.10  3.628 ±0.015-3.638 ± 0.015  8-10 (25.26-25.34) ± 0.10  3.515 ± 0.014-3.526 ±0.014 12-14 (25.81-25.89) ± 0.10  3.441 ± 0.013-3.452 ± 0.013 7-8(26.53-26.61) ± 0.10  3.350 ± 0.012-3.360 ± 0.012 11-11 (26.98-27.09) ±0.10  3.291 ± 0.012-3.305 ± 0.012 11-11 (27.55-27.63) ± 0.10  3.229 ±0.012-3.238 ± 0.012 11-13 (28.23-28.30) ± 0.10  3.154 ± 0.011-3.161 ±0.011 7-9 (28.87-28.97) ± 0.10  3.083 ± 0.010-3.093 ± 0.011  7-10(29.15-29.25) ± 0.10  3.053 ± 0.010-3.064 ± 0.010 10-11

TABLE 19 Prominent Peak Ranges for Rifaximin Form Mu Intensity Range °2θRange d Space Range (Å) (%)  (4.72-4.75) ± 0.10 18.597 ± 0.400-18.729 ±0.405 99-100  (4.79-4.82) ± 0.10 18.339 ± 0.388-18.467 ± 0.394 84-100 (7.84-7.86) ± 0.10 11.248 ± 0.145-11.272 ± 0.145 20-23  (8.11-8.13) ±0.10 10.879 ± 0.135-10.901 ± 0.136 55-77  (8.36-8.39) ± 0.10 10.533 ±0.127-10.575 ± 0.128 32-60  (8.55-8.56) ± 0.10 10.328 ± 0.122-10.348 ±0.122 44-53  (8.70-8.73) ± 0.10 10.130 ± 0.117-10.169 ± 0.118 44-57 (9.60-9.65) ± 0.10  9.167 ± 0.096-9.215 ± 0.097 13-17 (12.54-12.59) ±0.10  7.031 ± 0.056-7.059 ± 0.057 15-18

TABLE 20 Characterizations of Rifaximin Form Mu Analytical TechniqueResults³ ¹H-NMR Chemical structure intact 0.5 mole of ethanol per moleof API Chemical structure intact 0.6 mole of ethanol per mole of APIKarl-Fischer 14.1 wt % of water (approximately 7 moles) 12.7 wt % ofwater (approximately 6 moles) DSC Endo 92° C. (max), ΔH = 443.1 J/g TG15.7% wt loss up to 100° C. ATR-IR Spectrum acquired Raman Spectrumacquired Solid-State Spectrum acquired ¹³C NMR Moisture −11.0 % wtchange upon equilibration at Balance 5% RH 9.5% wt gain from 5%-95% RH9.3% wt lost from 95%-5% RH Post-MB Form γ XRPD³Endo=endotherm; wt=weight.

TABLE 21 Stress Study of Rifaximin Form μ XRPD Condition Observations⁴Result 60° C./Vacuum, ~24 hours Dark red blades, B/E γ 59-62° C./Vacuum,~24 hours Dark red solid γ 97% RH (RT), 16 days Orange μ + β⁴B=birefringent; E=extinction.

Example 5 Preparation of Form Gamma

Form Gamma is a hygroscopic crystalline mesophase. This formdemonstrates 1.2-3.8% weight loss by TGA and an endotherm atapproximately 203° C. (Table 4).

Rifaximin Form Gamma was obtained from solution in ethanol/watermixtures. Solids were obtained by crash cooling an ethanol/water(1/0.45) solution in an ice bath and air drying for 45 minutes and fromα Form α slurry in ethanol/water (1/0.5). TG analysis demonstrated a 1.2to 3.8% weight loss corresponding to a broad endotherm at 89° C. in theDSC curve. A minor endotherm, observed in both samples, at 203° C.Moisture balance sorption/desorption showed a 2.4% weight loss uponequilibration at 5% RH. The material is hygroscopic, gaining 10.8%weight under 95% RH. This weight (11.7%) was lost upon desorption to 5%RH. Long-term relative humidity studies of Form γ showed no formconversion when exposed to relative humidities from 11 to 94% for twodays. The form remained unchanged by XRPD analysis after drying undervacuum at ambient temperature for one day. Other methods are disclosedinfra, for example, in the Tables which follow.

Form Zeta

Form Zeta is a crystalline mesophase. The material was generated byslurrying Form Alpha dry in ethanol/water (1/0.45 at 0° C. and 1/1 atambient temperature) for two days. Recovered solids were allowed to airdry and stored under ambient conditions for three days. Form Zeta wasalso formed by storing Form ζ under 58 and 75% RH for three days. Othermethods are disclosed infra, for example, in the Tables which follow.

Example 6 Preparation of Form Zeta

Form ζ was observed by XRPD analysis of solids in solution (FIG. 42).These solids were removed and stressed under various RH conditions. XRPDanalysis after three days showed conversion to Form γ under 43% RH; Formγ-lunder 58 and 75% RH, and Form β+γ−1 under 94% RH, though formconversion was likely initiated upon removal of the solids fromsolution. Other methods are disclosed infra, for example, in the Tableswhich follow.

Example 7 Preparation of Form Eta

Form η was generated according to FIG. 53. Other methods are disclosedinfra, for example, in the Tables which follow. For example, as shown byFIG. 53, the Eta crystallization process consists of dissolution ofrifaximin in ethanol followed by cooling to a seeding temperature,adding a separately prepared slurry of Form Zeta seeds in ethanol at aseeding temperature, holding for one hour followed by cooling to asub-ambient temperature to generate a slurry of Form Zeta. The slurry isthen filtered, washed and dried.

Example 8 Preparation of Form Iota

Form ι was generated according to FIG. 53. Other methods are disclosedinfra, for example, in the Tables which follow. The space group wasdetermined to be P2₁2₁2₁. The packing motif of rifaximin Form Iota isdifferent than the layered arrangement observed in the previous twostructures. The crystal structure contained additional residual electrondensity, typically attributed to highly disordered solvent, in thelattice.

TABLE 22 Form η and Mixtures of Form η Initial Form Conditions FinalForm η vac oven, 40° C., 1 day η ζ vac oven, ambient, 1 day η ζ vac dryγ + η ζ vac oven, 45° C., 2 days η

TABLE 23 Crystallization from EtOH and EtOH/Water Mixtures XRPD SolventsConditions ^(a) Observations ^(b) Form EtOH slurry, ambient, 3 daysorange; fragments; ζ B&E a) SE, 5 days; orange; needle; ζ b) seeded withε B&E EtOH/H₂O slurry, ambient, 3 days orange; irregular; ζ 1/0.02 mLfragments; B&E EtOH/H₂O slurry, ambient, 3 days orange; fragments; ζ1/0.1 mL B&E EtOH/H₂O a) SC; refrigerator orange; needle; ζ 1/0.25 mL b)seeded with ε B&E Et0H/H₂O slurry, ambient, 5 hours — ζ 2/0.5 mLEtOH/H₂O control cooling: 3° C./h, in solution ζ 1/0.45 mL 70-20° C.crash cool in ice-water in solution ζ EtOH/H₂O slurry, 0° C., 2 days;light orange; small (ζ) 1/0.5 mL air-dried and stored at ambient needle;B&E 3 days slurry, ambient, 2 days; orange; small (ζ) air-dried andstored at ambient needles; B&E H₂O 3 days slurry (β-1), ambient, 1 days;light orange; air dried 7 h fragments; B&E α + β ^(a) SE = slowevaporation; SC = slow cooling. ^(b) B&E = birefringence and extinction.^(c) Samples were determined in solution in a capillary.

TABLE 24 Rifaximin Drying Experiments Starting XRPD Material ConditionsObservations a Form ζ stored in refrigerator 3 weeks — ζ ζ open vial inhood orange; small fragments; γ B&E ζ vac oven, ambient, 1 day orange;irregular; B&E η ζ vac oven, 45° C., 2 day sorange; fragments; B&E η ζair dry 2329-06-02a dark orange; irregular; B&E γ ζ vac dry 2329-06-02adark orange; irregular: B&E γ + η η vac oven, 40° C., 1 day orange;fragment; B&E η a. B&E = birefringence and extinction.

TABLE 25 Stressing Under Various Relative Humidities Form Conditions^(a)Observations XRPD Form α P₂O₅, 4 days dark orange; irregular particles;B&E α dry α dry 58% RH, 2 days light orange; small irregular particle;B&E β 75% RH, 2 days light orange; small irregular particle; B&E β 94%RH, 2 days light orange; small irregular particle; B&E β ζ 43% RH, 3days Orange; small particle; B&E γ 58% RH, 3 days Orange; smallparticle; B&E ζ 75% RH, 3 days Orange; small particle; B&E ζ 94% RH, 3days light orange; small particle; B&E β + ζ ζ stability chamber orange;needle; B&E ζ + γ 75% RH @40° C., 1 day ^(a)All samples stored at roomtemperature unless otherwise indicated; RH = relative humidity ^(b)B =birefringence; E = extinctionThe following techniques are described below, but are used throughoutthe examples.

Slow Evaporation (SE)

Solvent was added to weighed amounts of rifaximin in vials. Mixtureswere sonicated to achieve complete dissolution of solids. The solutionswere then filtered into clean vials. Solvents were slowly evaporated atambient conditions.

Crash Cool (CC)

A sample of rifaximin in ethanol/water 1/0.45 was prepared and passedthrough 0.2-μm nylon filter into a clean vial. The vial containing thesolution was then rapidly cooled by submersion in an ice bath forseveral seconds. Solids that precipitate were collected by filtrationand dried.

Slurry Experiments

Test solvents were added to rifaximin in vials such that excessundissolved solids were present in solutions. The mixtures were thanslurried on a shaker block or rotating wheel at subambient or roomtemperature.

Stressing Under Various Relative Humidities (RH)

A vial containing rifaximin was placed uncovered within a jar containingphosphorous pentoxide (P2O5) or a saturated salt solution in water. Thejar was sealed and stored at either ambient temperature or in an oven atelevated temperature.

Slow Cool (SC) Saturated solutions of rifaximin were prepared byslurrying excess solids in the test solvent at elevated temperature. Thesaturated solution was filtered while warm into a clean vial. The samplewas allowed to cool to room temperature, and then further cooled tosub-ambient temperature using a refrigerator, followed by a freezer.

Milling

A solid sample of rifaximin was charged to a milling container with amilling ball. Samples were milled for 5 or 15 minute intervals (2×5minutes, 2×15 minutes, and 3×15 minutes) at 30 Hz using a Retsch MM200mixer mill. Solids were scraped from the sides of the vial after eachinterval.

Optical Microscopy

Optical microscopy was performed using a Leica MZ12.5 stereomicroscope.Various objectives typically ranging from 0.8-4× were used withcrossed-polarized light to view samples. Samples were viewed in situ.

Thermal Analyses

Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry (DSC) was performed using a TAInstruments differential scanning calorimeter 2920. The sample wasplaced into an aluminum DSC pan, and the weight accurately recorded. Thepan was covered with a lid and then crimped or left uncrimped. Thesample cell was equilibrated at 25° C. and heated under a nitrogen purgeat a rate of 10° C./min, up to a final temperature of 250 or 350° C.Indium metal was used as the calibration standard. Reported temperaturesare at the transition maxima.

Method A: initial equilibration at 25° C., heated to 250° C. at 10°C./min

Method B: initial equilibration at 25° C., heated to 350° C. at 10°C./min

Cyclic Differential Scanning calorimetry

Cyclic DSC was performed using a TA Instruments 2920 differentialscanning calorimeter. The sample was placed into a hermetically sealedDSC pan, and the weight accurately recorded. The pan was covered with alid containing a laser pinhole. The method was as follows:

1. Equilibrate at −50° C.

2. Ramp 20° C./min to 80° C.

3. Isothermal at 80° C. for 1 min

4. Equilibrate at −50° C.

5. Ramp 20° C./min to 220° C.

Indium metal was used as the calibration standard. Reported temperatureis at the transition maxima.

Dynamic Vapor Sorption (DVS)

Automated vapor sorption (VS) data were collected on a VTI SGA-100 VaporSorption Analyzer. NaCl and PVP were used as calibration standards.Samples were not dried prior to analysis. Sorption and desorption datawere collected over a range from 5 to 95% RH at 10% RH increments undera nitrogen purge. The equilibrium criterion used for analysis was lessthan 0.0100% weight change in 5 minutes with a maximum equilibrationtime of 3 hours. Data were not corrected for the initial moisturecontent of the samples.

Hot-Stage Microscopy

Hot stage microscopy was performed using a Linkam hot stage (FTIR 600)with a TMS93 controller mounted on a Leica DM LP microscope equippedwith a SPOT Insight™ color digital camera. Temperature calibrations wereperformed using USP melting point standards. Samples were placed on acover glass, and a second cover glass was placed on top of the sample.As the stage was heated, each sample was visually observed using a20×0.4 N.A. long working distance objective with crossed polarizers anda first order red compensator. Images were captured using SPOT software(v. 4.5.9).

Modulated Differential Scanning calorimetry (MDSC)

Modulated differential scanning calorimetry (MDSC) data were obtained ona TA Instruments differential scanning calorimeter 2920 equipped with arefrigerated cooling system (RCS). The sample was placed into analuminum DSC pan, and the weight accurately recorded. The pan wascovered with a lid perforated with a laser pinhole to allow for pressurerelease, and then hermetically sealed. MDSC data were obtained using amodulation amplitude of +/−0.8° C. and a 60 second period with anunderlying heating rate of 1° C./min from 25-225° C. The temperature andthe heat capacity were calibrated using indium metal and sapphire as thecalibration standards, respectively. The reported glass transitiontemperatures are obtained from the half-height/inflection of the stepchange in the reversible heat flow versus temperature curve.

Thermogravimetric (TG) Analyses

Thermogravimetric (TG) analyses were performed using a TA Instruments2950 thermogravimetric analyzer. Each sample was placed in an aluminumsample pan and inserted into the TG furnace. The furnace was firstequilibrated at 25° C. or started directly from ambient temperature,then heated under nitrogen at a rate of 10° C./min, up to a finaltemperature of 350° C. Nickel and Alumel™ were used as the calibrationstandards. Methods for specific samples are referred to as summarizedbelow

-   -   Method A: no initial equilibration; analysis started directly        from ambient, sample heated to 350° C. at 10° C./min    -   Method B: initial equilibration at 25° C., sample heated to        350° C. at 10° C./min    -   Method C: no initial equilibration; analysis started directly        from ambient, sample heated to 300° C. at 10° C./min

Spectroscopy

Fourier Transform Infrared (FT-IR)

The IR spectra were acquired on a Magna-IR 860® Fourier transforminfrared (FT-IR) spectrophotometer (Thermo Nicolet) equipped with anEver-Glo mid/far IR source, an extended range potassium bromide (KBr)beamsplitter, and a deuterated triglycine sulfate (DTGS) detector. Anattenuated total reflectance (ATR) accessory (the Thunderdome™, ThermoSpectra-Tech), with a germanium (Ge) crystal was used for dataacquisition. The spectra represent 256 co-added scans collected at aspectral resolution of 4 cm⁻¹. A background data set was acquired with aclean Ge crystal. A Log 1/R (R=reflectance) spectrum was acquired bytaking a ratio of these two data sets against each other. Wavelengthcalibration was performed using polystyrene.

Fourier Transform Raman (FT-Raman)

FT-Raman spectra were acquired on a Raman accessory module interfaced toa Magna 860® Fourier transform infrared (FT-IR) spectrophotometer(Thermo Nicolet). This module uses an excitation wavelength of 1064 nmand an indium gallium arsenide (InGaAs) detector. Approximately 0.6-2.0W of Nd:YVO₄ laser power was used to irradiate the sample. The sampleswere prepared for analysis by placing the material in a glass tube andpositioning the tube in a gold-coated tube holder in the accessory. Atotal of 256 or 1024 sample scans were collected from 98-3600 cm⁻¹ at aspectral resolution of 4 cm⁻¹, using Happ-Genzel apodization. Wavelengthcalibration was performed using sulfur and cyclohexane.

Peak Picking of IR and Raman Spectra

Peak picking was performed using Omnic version 7.2.

Peak position variabilities are given to within ±2 cm-1, based on theobserved sharpness of the peaks picked and acquisition of data using a 2cm-1 data point spacing (4 cm-1 resolution). Third party measurements onindependently prepared samples on different instruments may lead tovariability which is greater than ±2 cm-1.

Automated Moisture Sorption/Desorption

Moisture sorption/desorption data were collected on a VTI SGA-100 VaporSorption Analyzer. Sorption and desorption data were collected over arange of 5% to 95% relative humidity (RH) at 10% RH intervals under anitrogen purge. Samples were not dried prior to analysis. Equilibriumcriteria used for analysis were less than 0.0100% weight change in 5minutes, with a maximum equilibration time of 3 hours if the weightcriterion was not met. Data were not corrected for the initial moisturecontent of the samples. NaCl and PVP were used as calibration standards.

Karl-Fischer Titration (KF)

Coulometric Karl Fischer (KF) analysis for water determination wasperformed using a Mettler Toledo DL39 KF titrator. A blank titration wascarried out prior to analysis. The sample was prepared under a drynitrogen atmosphere, where approximately 1 gram of the sample weredissolved in approximately 1 mL dry Hydranal-Coulomat AD in a pre-driedvial. The entire solution was added to the KF coulometer through aseptum and mixed for 10 seconds. The sample was then titrated by meansof a generator electrode, which produces iodine by electrochemicaloxidation: 2 I⁻→I₂+2e⁻.

Solution 1D ¹H NMR Spectroscopy (SSCI)

The solution NMR spectra were acquired with a Varian ^(UNITY)INOVA-400spectrometer. The samples were prepared by dissolving approximately 5 to10 mg of sample in CDCl₃ containing TMS.

Solution 1D ¹H NMR Spectroscopy (SDS, Inc.)

One solution ¹H NMR spectrum was acquired by Spectral Data Services ofChampaign, Ill. at 25° C. with a Varian ^(UNITY)INOVA-400 spectrometerat a ¹H Larmor frequency of 399.796 MHz. The samples were dissolved inCDCl₃. The spectra were acquired with a ¹H pulse width of 6.0 μs, a 5second delay between scans, a spectral width of 10 KHz with 35K datapoints, and 40 co-added scans. The free induction decay (FID) wasprocessed with 64K points and an exponential line broadening factor of0.2 Hz to improve the signal-to-noise ratio.

Solid State ¹³C Nuclear Magnetic Resonance (NMR)

Samples were prepared for solid-state NMR spectroscopy by packing theminto 4 mm PENCIL type zirconia rotors.

The solid-state ¹³C cross polarization magic angle spinning (CP/MAS) NMRspectra were acquired at ambient temperature on a Varian^(UNITY)INOVA-400 spectrometer (Larmor frequencies: ¹³C=100.542 MHz,¹H=399.787 MHz). The sample was packed into a 4 mm PENCIL type zirconiarotor and rotated at 12 kHz at the magic angle. The chemical shifts ofthe spectral peaks were externally referenced to the carbonyl carbonresonance of glycine at 176.5 ppm.

Example 9 Alternative Preparation Methods for Select Rifaximin Forms

Rifaximin Form Zeta

Rifaximin (404.5 mg) was slurried in an ethanol/water mixture (2 mL/0.5mL) at ambient temperature for approximately 5 hours. Solvent wasremoved by decantation and the damp solids stored in the refrigeratorfor less than one day prior to analysis by XRPD. Solids were damp priorto and after XRPD analysis. (FIG. 43)

Rifaximin Form Eta

After a portion of the rifaximin was removed for XRPD analysis theremainder of the sample was dried under vacuum at ambient temperaturefor approximately one day. Solids were stored in a dessicator prior toanalysis by XRPD. (FIG. 45).

The method of forming Eta, shown in FIG. 54, consists of dissolution ofRifaximin (of any solid form) in ethanol followed by cooling to aseeding temperature, adding a separately prepared slurry of Form Zetaseeds in ethanol at the seeding temperature, holding for one hourfollowed by cooling to sub-ambient temperature to generate a slurry ofForm Zeta. The slurry is then filtered, washed and dried. Thecrystallization process includes the filtration and washing steps.Certain embodiments of the Rifaximin Form Eta processes are to 1)control the solid form of the dried material to Form Eta, and 2) producea high yield. The following parameters may influence the dried solidform and yield:

-   -   Water content in the Rifaximin starting material    -   Water content in ethanol    -   Rifaximin concentration    -   Final temperature    -   Hold time at final temperature    -   Wash composition    -   Exposure time of filter cake to atmosphere    -   Drying temperature    -   Drying pressure    -   Drying time

Seeding and cooling rate parameters do not appear to be involved incontrolling the ‘wet’ form under the conditions investigated.

X-Ray Powder Diffraction (XRPD)

Inel XRG-3000 Diffractometer

X-ray powder diffraction (XRPD) analyses were performed using an InelXRG-3000 diffractometer equipped with a CPS (Curved Position Sensitive)detector with a 2θ range of 120°. Real time data were collected usingCu-K α radiation. The tube voltage and amperage were set to 40 kV and 30mA, respectively. The monochromator slit was set at 1-5 mm by 160 μm.The patterns are displayed from 2.5-40° 2 θ. Samples were prepared foranalysis by packing them into thin-walled glass capillaries. Eachcapillary was mounted onto a goniometer head that is motorized to permitspinning of the capillary during data acquisition. The samples wereanalyzed for 300 seconds. Instrument calibration was performed using asilicon reference standard.

PANalytical X'Pert Pro Diffractometer

Samples were also analyzed using a PANalytical X'Pert Prodiffractometer. The specimen was analyzed using Cu radiation producedusing an Optix long fine-focus source. An elliptically graded multilayermirror was used to focus the Cu K α X-rays of the source through thespecimen and onto the detector. The specimen was sandwiched between3-micron thick films, analyzed in transmission geometry, and rotated tooptimize orientation statistics. A beam-stop and a helium purge wereused to minimize the background generated by air scattering. Sollerslits were used for the incident and diffracted beams to minimize axialdivergence. Diffraction patterns were collected using a scanningposition-sensitive detector (X'Celerator) located 240 mm from thespecimen to the analysis a silicon specimen (NIST standard referencematerial 640c) was analyzed to verify the position of the silicon 111peak.

TABLE 26 XRPD Peak Positions of Rifaximin Form Zeta Position (°2θ)I/Io^(a)  4.7 (doublet) 86  6.3 8  6.4 16  7.3 25  7.6 (doublet) 100 8.2 10  8.6 20  9.5 12 10.2 (triplet) 6 10.5 4 11.2 (doublet) 3 11.9(doublet) 5 12.2 (weak) 5 12.6 (quintet) 16 12.9 (doublet) 7 13.2(doublet) 5 ^(a)I/I_(o) = relative intensity.

TABLE 27 XRPD Peak Positions of Rifaximin Form Eta Position (°2θ)I/Io^(a) 5.3 28 6.1 71 7.3 24 7.5 28 7.9 100 8.8 76 12.7 34 ^(a)I/I_(o)= relative intensity.

TABLE 28 Form Iota Methods of Making the Form Iota of Rifaximin XRPDSolvent Conditions Observation Result Methanol CC red orange, blades,single ι and in spherulites, birefringent SC red orange, dendridic ιformations, birefringent

Example 10 Crystallization, Isolation & Drying Crystallization to ObtainForm Eta

The process for production of Form eta is set forth in flow chart 1(FIG. 11).

A slurry of Rifaximin form zeta was prepared by stirring 33.4 gRifaximin in 150 ml absolute ethanol for approximately 5 h. The seedslurry was prepared by stirring 500 mg of Rifaximin in 10 ml absoluteethanol at ambient for approximately 2 h. The Rifaximin slurry wascharged to a 250 ml controlled laboratory reactor and dissolved byheating to 60° C. and holding while stirring at 300 rpm for 15 min. Thesolution was cooled to 40° C. over 30 min, then the seed slurry wasadded and held stirring at 40° C. for 60 min. The mixture was, cooled to0 C at −0.2° C./min (200 min) and held for approximately 14 h. Theslurry was then discharged into a Buchner funnel for filtration.Approximately 50 ml of chilled absolute ethanol (chilled over ice) wasadded to the reactor to rinse out the remaining particles and set aside.The slurry was filtered with vacuum to dry land then reactor rinse wasadded and filtered to dry land followed by the addition of 1 cake volumeof chilled absolute ethanol. Vacuum filtration of the damp filter cakewas continued for approximately 30 min. The filter cake was transferredto a crystallizing dish, covered with porous paper and dried in a vacuumoven at 40° C. for approximately 24 h. Yield=88%, LOD=27%, Form Eta(XRPD), 2.0% weight loss (TGA), 1.66% residual ethanol (H NMR). 0.82%water (KF).

While some embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. For example, for claimconstruction purposes, it is not intended that the claims set forthhereinafter be construed in any way narrower than the literal languagethereof, and it is thus not intended that exemplary embodiments from thespecification be read into the claims.

Accordingly, it is to be understood that embodiments have been describedby way of illustration and do not limit the scope of the claims.

What is claimed is:
 1. A form of rifaximin selected from one or more ofForm Mu, Form Pi, Form Xi, Form Omicron, Form Xi or a salt, or hydrateform thereof.
 2. The Form Mu of claim 1, having an X-ray powderdiffraction comprising peaks, in terms of 2θ, at two or more of about4.72, about 4.79, about 7.84, about 8.11, about 8.36, about 8.55, about8.70, about 9.60, and about 12.54.
 3. The Form Mu of claim 1, having anX-ray powder diffraction comprising peaks, in terms of 2θ, at two moreof about 4.72, about 4.79, about 6.29, about 6.94, about 7.44, about7.84, about 8.11, about 8.36, about 8.55, about 8.70, about 8.88, about9.60, about 10.15, about 10.32, about 10.88, about 11.02, about 11.20,about 12.09, about 12.54, about 12.79, about 12.96, about 13.42, about13.63, about 13.86, about 14.54, about 14.90, about 15.25, about 15.50,about 16.00, about 16.30, about 16.62, about 16.78, about 16.97, about17.27, about 17.47, about 17.57, about 17.84, about 18.20, about 18.57,about 18.97, about 19.42, about 19.88, about 20.78, about 21.76, about22.18, about 22.52, about 22.83, about 23.27, about 23.70, about 24.17,about 24.47, about 24.67, about 25.26, about 25.81, about 26.53, about26.98, about 27.55, about 28.23, about 28.50, about 28.87, and about29.15.
 4. The Form Mu of claim 1, comprising an X-ray powder diffractionsubstantially similar to one or more of FIGS. 1-3.
 5. The Form Mu ofclaim 1, comprising an X-ray powder diffraction substantially similar toone or more of FIGS. 1-8 and one or more of Tables 1-9.
 6. The Form Piof claim 1, comprising an X-ray powder diffraction substantially similarto one or more of FIGS. 9 and 12-14.
 7. The Form Pi of claim 1, havingan X-ray powder diffraction comprising peaks, in terms of 2θ, at about6.91 and about 7.16.
 8. The Form Pi of claim 1, having an X-ray powderdiffraction comprising peaks, in terms of 2θ, at about 7.05 and about7.29.
 9. The Form Pi of claim 1, having an X-ray powder diffractioncomprising peaks, in terms of 2θ, at two or more of about 7.05, about7.29, and about 9.33.
 10. The Form Pi of claim 1, having an X-ray powderdiffraction comprising peaks, in terms of 2θ, at about 6.91-7.05 andabout 7.16-7.29.
 11. The Form Pi of claim 1, having an X-ray powderdiffraction comprising peaks, in terms of 2θ, at about 6.91-7.05, about7.16-7.29, and about 9.15-9.33.
 12. The Form Omicron of claim 1,comprising an X-ray powder diffraction substantially similar to FIG. 11.13. The Form Omicron of claim 1, comprising an X-ray powder diffractioncomprising the peaks in FIG.
 11. 14. The Form Omicron of claim 1,comprising and XRPD substantially similar to one or more of FIGS. 32,34, and
 37. 15. The Form Omicron of claim 1, having an X-ray powderdiffraction comprising peaks, in terms of 2θ, at two or more of about5.87, about 6.99, and about 8.31.
 16. The Form Omicron of claim 1,having an X-ray powder diffraction comprising peaks, in terms of 2θ, attwo or more of about 5.87, about 6.99, about 8.31, about 9.13, about13.27, about 13.69, and about 17.67.
 17. The Form Omicron of claim 1,having an X-ray powder diffraction comprising peaks, in terms of 2θ, attwo or more of about 5.87, about 6.99, about 7.77, about 8.31, about8.47, about 9.13, about 9.58, about 9.74, about 10.86, about 12.35,about 13.27, about 13.69, about 14.01, about 14.44, about 14.79, about15.19, about 15.33, about 15.68, about 15.94, about 16.04, about 16.31,about 16.66, about 17.00, about 17.35, about 17.67, about 18.08, about19.04, about 19.24, about 19.52, about 19.85, about 20.17, about 20.42,about 20.76, about 21.07, about 21.28, about 21.61, about 21.83, about22.14, about 22.36, about 22.65, about 22.93, about 23.20, about 23.46,about 23.71, about 24.15, about 24.35, about 24.67, about 25.07, about25.40, about 25.80, about 26.22, about 26.54, about 26.76, about 27.17,about 27.78, about 28.69, about 28.88, about 29.21, about 29.46, about23.71, about 24.15, about 24.35, about 24.67, about 25.07, about 25.40,about 25.80, about 26.22, about 26.54, about 26.76, about 27.17, about27.78, about 28.69, about 28.88, about 29.21, and about 29.46.
 18. AForm of rifaximin according to claim 1, wherein the rifaximin Formcontains less than 5% by weight impurities.
 19. A Form of rifaximinaccording to claim 1, wherein one or more of the rifaximin forms is atleast 50% pure, at least 75% pure, at least 80% pure, at least 90% pure,at least 95% pure, or at least 98% pure.
 20. A Form of rifaximinaccording to claim 1, wherein one or more of the rifaximin forms areformulated as coated or uncoated tablets, hard or soft gelatin capsules,sugar-coated pills, lozenges, wafer sheets, pellets, or powders insealed packet.
 21. A pharmaceutical composition comprising one or moreforms of rifaximin according to claim 1, and a pharmaceuticallyacceptable carrier.
 22. A method of treating, preventing, or alleviatinga bowel related disorder, comprising administering to a subject in needthereof and effective amount of one or more forms of rifaximin accordingto claim 1, comprising one or more steps as disclosed herein.
 23. Amethod of producing one or more of forms of rifaximin according to claim1, comprising one or more steps as disclosed herein.
 24. A method ofproducing rifaximin Form Eta, comprising: dissolving a Form of rifaximinto form a first mixture; cooling the first mixture to a seedingtemperature; adding a slurry of rifaximin Form Zeta to form a secondmixture; cooling the second mixture to sub-ambient temperature; andfiltering the second mixture to obtain Form Eta, which is optionallywashed and dried.
 25. The method of claim 24, wherein the Form ofrifaximin comprises a solid form.
 26. The method of claim 24, whereinthe Form of rifaximin is selected from Form Mu, Form Pi, Form Alpha,Form Beta, Form Xi, Form Nu, Form Theta, Form Gamma, Form Omicron, FormZeta, or a salt, or mixtures thereof.
 27. The method of claim 24,wherein the Form of rifaximin is Form Zeta.
 28. The method of claim 24,wherein the first mixture comprises ethanol.
 29. The method of claim 28,wherein the water content of the first mixture is higher thanapproximately 3 wt %.
 30. The method of claim 29, wherein the watercontent of the first mixture ranges from about 3 wt % to about 10 wt %.